Method of reducing spectral density of photodiode diffusion current fluctuation in high frequency range

FIELD: physics.

SUBSTANCE: method of reducing spectral density of photodiode diffusion current fluctuation in high frequency range involves applying reverse bias V across a p-n junction with a short base and a blocking contact to the base, said reverse bias satisfying the conditions 3kT < q|V| < Vb,t and 3kt < q|V| < Vb,a, where: k is Boltzmann constant; T is temperature; q is electron charge; Vb,t is tunnel breakdown voltage; Vb,a is avalanche breakdown voltage.

EFFECT: disclosed method enables to increase the signal-to-noise ratio of the photodiode in the high frequency range by reducing spectral range of diffusion current fluctuation.

4 dwg

 

The invention relates to photoelectronics and can be used in threshold photodetector devices for registration of short pulses (∆t < τwhere∆t isthe pulse duration ofτ -the lifetime of nonequilibrium charge carriers in the photodiode) electromagnetic radiation in the optical and infrared range.

Fluctuations in the dark current and photocurrent are the fundamental factors limiting threshold characteristics and operating temperature IR photodetectors. The dark current HgCdTe photodiodes far IR range at cryogenic temperatures, as well as photodiodes middle IR range, operating at elevated temperatures, is determined by the diffusion mechanism. While the diffusion currentp - ntransitions with a short base (d < Lwhered- the thickness of the base, andLthe diffusion length of minority charge carriers) will depend largely on the type of contact (boundary conditions) to the database. Thus, in the known method [1] withthe diffusion currentp - ntransition with a short base and a blocking contact ind/Ltimes smaller than the diffusion current is the same asp - ntransition with a long base. However, the use of a blocking contact to reduce the spectral density of fluctuations (PCF) diffusion current proven in a known way to reduce spectral the density fluctuations of the diffusion current of the photodiode [1], taken as a prototype, only for low frequencies (ωτ << 1, where ω is circular frequency modulation of radiation). The exact calculation of the SPF diffusion currentp - ntransitions with a short base in a wide frequency range based on the Langevin method is executed only at the present time in [2].

The task of the invention is to increase the signal-to-noise photodiodes in the field of high frequencies (ωτ > 1) by reducing the spectral density of fluctuations of the diffusion current.

The technical result is achieved by a method for reducing spectral density of fluctuations of the diffusion current of the photodiode in the field of high frequencies, namely, thatp - nthe transition from the short base (d < L,whered- the thickness of the base, andL- the diffusion length of minority carriers in the base) and a blocking contact to the base serves reverse biasVsatisfying the conditions

3kT<q|V| <Vb,tand 3kT<q|V| <Vb,a,

wherekis the Boltzmann constant;

Ttemperature;

q- the charge of the electron;

Vb,t- voltage tunneling breakdown;

Vb,a- voltage avalanche breakdown.

The proposed invention is illustrated by calculations and graphs of the dependencies.

Figure 1 shows the SPF diffusion currentp+ - nthe transition from the base of finite length and an ohmic contact tonarea. Solid lines correspond to the normalized SPF diffusion current, dashed - normalized additive components SPF diffusion current due to the random nature of the scattering processes, phantom normalized additive components SPF diffusion current due to the random nature of the processes of thermal generation and recombination. Normalizing the value ofthe relationd/Lp= 0.5. Inset shows the structure of the consideredp+- ntransition.

Figure 2 shows SPF diffusion currentp+- nthe transition from the base of finite length and the blocking contact tonarea. Solid lines correspond to the normalized SPF diffusion current, dashed - normalized additive components SPF diffusion current due to the random nature of the scattering processes, phantom normalized additive components SPF diffusion current due to the random nature of the processes of thermal generation and recombination. Normalizing the value ofthe relationd/Lp= 0.5.

In Fig. 3 shows SPF diffusion current obratno.slishal ()p+- nthe transition length is Noah base. The solid line corresponds to the normalized SPF diffusion current, dashed - normalized additive component SPF diffusion current due to the random nature of the scattering processes, phantom normalized additive component SPF diffusion current due to the random nature of the processes of thermal generation and recombination. Normalizing the value of.

In Fig. 4 shows SPF diffusion currentp+- ntransitions with different structure: SPF diffusion currentp+- nthe transition from the base of finite length and an ohmic contact tonregion, SPF diffusion currentp+- ntransition with a long base, SPF diffusion currentp+- nthe transition from the base of finite length and the blocking contact tonarea. Solid lines correspond to the normalized SPF diffusion current, dashed - normalized additive components SPF diffusion current due to the random nature of the scattering processes, phantom normalized additive components SPF diffusion current due to the random nature of the processes of thermal generation and recombination. Normalizing the value ofthe relationd/Lp= 0.5,V= 0.

RAS is read SPF diffusion current p - ntransition with a short base for the case of ohmic and blocking contact to the case of small displacements of either polarity method Langevin. Initially, we analyze the stationary model. Consider- ntransition, the dark current which is determined by the processes of thermal generation and recombination in the quasi-neutralnregion and on which is supported a small constant offsetarbitrary polarity (forward or reverse) Fig. 1. Such structure havep - ntransitions based on HgCdTe grown by molecular-beam epitaxy [3], and also made by low-energy ion treatment [4]. We will consider the case when a forward bias- ntransition, as well as when exposed to incident radiation is approaching a low level injection. Note that in this approximation the recombination of holes in thenthe area can be considered in the framework of linear models, and modulation of the conductivity ofnthe field can be neglected.

However, we will restrict ourselves to the analysis of the case of not too large reverse biases discussed- nof transition, in which it is possible to neglect the interband tunnel current and the current due to tunneling through the trap, and so the e-impact ionization processes, i.e. we assume that conditions areq|V| <Vb,tandq|V| <Vb,a,whereVb,t- voltage tunneling breakdown,Vb,a- voltage avalanche breakdown. We will assume negligible internal resistance of the DC voltage on the diode, i.e. we assume the external circuit of the diode is short-circuited. We will also assume negligible series resistancenthe field that allows us not to consider in the futurelimitations of frequency characteristics- nof the transition. We will consider the situation, whenp - nthe transition falls monochromatic radiation fromregion, and this will make the assumption that the reflection from the surface of thep - ntransition can be neglected. We also assume that the thickness of thepregion, as well as the thickness of the space charge region (SCR) is extremely small, resulting in the absorption of radiation in these areas can be neglected.

Will send the axisxfromnregion, whose thickness is equal todtoarea and pointposition at the interface atnregion and the SCR (see inset in Fig. 1). We will consider the cases short where- the diffusion length of holes innarea,τthe lifetime of holes innareais the diffusion coefficient of holes) and long (base, as well as two types of contact (boundary conditions) at the point- ohmic and blocking. For calculating the steady-state concentration of holesin the quasi-neutralnthe area in question- nit is necessary to solve the continuity equation in ambipolar form, which, using the assumptions of the linear model of recombination, is

,

wherethe concentration of nonequilibrium holes innarea,

the equilibrium concentration of holes innarea,

is the absorption coefficient,

the flux density of photons of the incident radiation.

In the case of ohmic contact boundary condition to equation (1) at the pointisand , in the case of a blocking contact boundary condition at this point is.

At the pointthe boundary condition to uravnenii who (1) has the form [5],

where.

The distribution of the concentration of holes in the quasi-neutralnthe area and density of the total current is considered- ntransitionandaccordingly, for the case of ohmic contact tonregion, as well asandaccordingly, for the case of a blocking contact tonthe field can be represented as a sum of two terms

The first components of these equations are determined by the processes of thermal generation and recombination in the quasi-neutralnthe field in the absence of illumination,,,and are defined by the expression

(2)

(3)

(4)

(5)

where. Note thatandrepresent the density of the diffusion current under consideration- ntransition for the case of ohmic and blocking the ontact to nregion, respectively.

The second summands expressions foranddue to exposure to incident radiation and is determined by the expression

(6)

(7)

(8)

(9)

andrepresent the density of the photocurrent under consideration- ntransition for the case of ohmic and blocking contact tonregion, respectively. Calculations show that at the pointthere are finite limits of expressions (7) and (9). Whenexpressions (7) and (9) become the well-known formula for the density of the photocurrentp - ntransition with a long basewhere- the quantum efficiency of the photodiode [1, 6].

Consider now the stochastic model. Under the assumptions made in the analysis of fluctuation phenomena in question- nthe transition can be limited to the solution of the Langevin equation in ambipolar form. The formal procedure of conclusion of such equations [7] a similar procedure output determenirovana the equation of continuity in ambipolar form. In this case, quasi-neutralthe field of the Langevin equation in ambipolar form is

whereThe Fourier transformant fluctuations in the concentration of holes,

- circular frequency,

- kinetic diffusion length of holes innarea,

iis the imaginary unit,

The Fourier transformant random source corresponding to the random nature of the process of thermal generation and recombination,

The Fourier transformant random source corresponding to the random nature of the process of photogeneration,

The Fourier transformant random source corresponding to the random nature of the scattering processes.

Note that the analysis of fluctuations in ohmic resistor in the case, when considering only a random source that corresponds to the random nature of the scattering processes, leads to the well-known Nyquist formula for thermal noise [7].

In the case of ohmic contact (infinite surface recombination velocities) at the pointthe concentration of nonequilibrium carriers at a given point is equal to zero, which is true of the AK in a determined way, and in the case of fluctuations. Therefore, in the case of the ohmic contact, the stochastic boundary condition has the form. Note that the assumption of zero surface recombination velocities at the pointmeans no surface random source, due to the random nature of the processes of thermal generation and recombination at this point. Therefore, in the case of a blocking contact (zero surface recombination velocities) at the pointfluctuations hole current at this point is equal to zero. We will also assume that at the pointno surface scattering, and therefore, no surface random source, due to the random nature of the scattering processes.

Thus, in the case of a blocking contact at the pointfluctuation of the hole current and the fluctuation of the concentration of holes at this point connected by the relationand stochastic boundary condition has the form. Note that at the pointstationary and stochastic boundary conditions on the form are the same.

Will prove now the statement of the boundary conditions at the point.IN case when- nthe transition is supported by a reverse bias, satisfying the conditionthe current in the external circuit such- ntransition is determined by the processes of heat generation and photogeneration in the quasi-neutralnarea. When this electron-hole pairs formed in the quasi-neutralnthe field and reached the interface with the SCR, quickly separated by the electric field. Thus, in the present case, obratno.slishal- ntransition at the pointyou can put a stochastic boundary condition[8], valid in the frequency rangewherethe time of passage holes through the SCR due to drift in the electric field- nof the transition. In Annex I of [2] shows that for- ntransition-based ternary solid solution Hg1-xCdxTe ()formed by low-energy ion processing [4], is a fair assessmentC. note that the rapid separation of electron-hole pairs formed in thenthe field due to heat generation and photogenetic and reach boundaries with OPZ, also will take place in the case when- ntransition applied a small forward or a small reverse bias. Moreover, the evaluation time of passage holes through the SCR due to drift in the electric field- ntransition given in Annex I of [2], in this case, will also remain true.

In the case whenp+- ntransition applied a small forward or reverse bias, the holes diffusing fromp+the field can overcome the potential barrier in the SCR and get intonregion. According to theory ofp - ntransition developed by Shockley [9], while not very large direct and reverse offsets, through SCR consideredp+- ntransition flow in two opposite hole current - diffusion and drift significantly, by several orders of magnitude greater than the current in the external circuitp+- nof the transition. The flow of holes passing innregion and, consequently, the current in the external circuit framemasterp+- ntransition significantly less flow holes diffusing fromp+area, as limited by recombination in thenregion.

Thus, at the interface OPZ - atnregion instead progettogiovani intonthe area of the hole almost instantly in Snicket new, and the concentration of holes remains constant. From this it follows that in the case framemasterp+- ntransition, and in the case of small reverse bias at the pointyou can put a stochastic boundary conditionfair in the frequency rangewherethe time of passage through the SCR holes diffusing fromp+thep+- ntransition.

In Appendix II of [2] shows that in the considered case of small direct and small reverse offsets for time-of-flight through the SCR holes diffusing fromp+thep+- ntransition fair, the same evaluation as that for the time span of the holes through the SCR due to drift in the electric fieldp+- ntransition, i.e.

Thus, at small forward and backward movements in a fairly wide frequency rangeat the pointtrue stochastic boundary condition. Note that at the pointstationary and stochastic boundary conditions do not coincide in form with stochastic boundary condition does not depend on the applied voltage

p> The solution of equation (10) for the case of ohmic and blocking contactandrespectively, is easy. In the quasi-neutralnthe area of the Fourier transformant fluctuations of the density of hole current is determined by the equation

[7].

We substitute in it the solution of equation (10) and calculate the values of the Fourier transformant of the respective densities of the hole currentand. Then putget expressions for the Fourier transformant density fluctuations of the total current isp+- nthe transition from the base of finite length, to which is attached a small offset of arbitrary polarity under the action of the incident radiation for the case of ohmic and blocking contactandrespectively

(11)

(12)

Let us calculate now SPF diffusion current. Fluctuations of the total current is considered- ntransition represent a stationary random process, spectral PL is tnost fluctuations (SPF) of which associated with the Fourier transformed fluctuationsratio [10]

(13)

wheremeans complex conjugation,

- averaging over the ensemble,

- the Delta-function.

Random sources,andare Delta-correlated spatial coordinates inhomogeneous stationary random fields. Thus, for Fourier transformant random sources,andand the corresponding mutual SPF,andfair correlations, similar to equation (13). When this mutual SPF random sources, corresponding to the random nature of the processes of thermal generation and recombination, photogeneration and scattering respectively [7, 8]

(14)

(15)

(16)

Note that in expressions (14) - (16) are mutual SPF defined for positive frequencies,

which makes sense, since the real part of the mutual SPF associated stationary real random processes is an even function of frequency [11]. The latter is also true for SPF valid random processes [10]. Therefore, further we will consider only positive frequencies and determine the SPF of the total current at positive frequencies ratio. Note also that random sources,andare not correlated among themselves.

Equation (13), and the ratio(11), (12), (14) - (16), (2), (4), (6), (8) after a simple, but quite cumbersome transformations, performed by the computer algebra programs, allow the calculation of the SPF of the total current is considered- nof the transition. While the right and left side of equation (13) after substituting in him ratios(11), (14) - (16), (2), (6), for the case of ohmic contact, or(12), (14) - (16), (4), (8), for the case of a blocking contact, must be averaged over the areap - ntransitionA.

Because random sourcesandare not correlated, SPF total current will include three additive components ,

the first of which is due to random sourcei.e. the random nature of the processes of thermal generation and recombination, the second is due to random sourcei.e. the random nature of the processes of photogeneration, and the third random sourcei.e. the random nature of the scattering processes. However, due to the linearity of the model considered additive components SPF total currentandwill include components due to fluctuation processes that do not depend on illumination (tenovymi noises)andaccordingly, and components due to photoinduced fluctuation processesandaccordingly, i.e,.

The additive component of affiliate total currentdue solely to fluctuations of the process of photogeneration (see equation (15)). Thus, the SPF of the total current is considered- ntransition can be written as the sum of two values

(17)

where the value of due tenovymi noises and is an affiliate of the diffusion current, and the value ofdue to photoinduced noises and is an affiliate of the photocurrent.

SPF diffusion current under consideration- ntransition with a short base for the case of ohmic and blocking contact tontheandaccordingly determined by the expression

Frequency dependent magnitudeandin formulas (24) - (29) are defined by the expression

(20)

(21)

From formulas (20) and (21) it follows that in this caseandsatisfy the inequalitiesandaccordingly, i.e. the pointandwhere the expression (18), (19) have features that lie outside the tolerance range. Note that if() there are finite limits of expressions(18), (19).

The expression for the additive components of the SPF diffusion current - nthe transition from the base of finite length, due to the random nature of the processes of thermal generation and recombination, and random nature of the scattering processes, for the case of ohmic and blocking contact to theandandandaccordingly, it is very cumbersome, so we will restrict ourselves to the study of the limiting values of these PCF.

Let us calculate now the values of the additive components of the SPF diffusion current- nthe transition from longbase, due to the random nature of the processes of thermal generation and recombinationand scattering.

The results have the form

(22)

(23)

From equations (22) and (23) it follows that in the region of applicability of the obtained resultsSPF diffusion current is consideredp+- nthe transition from longbaseis determined by the expression

(24)

It is easy to check that the expression (24) is in full accordance with the expression for the spectral density of the noise ideal the second diode, obtained in the monograph [11] methods of theory of random pulses. Thus, the expression (24) is a form of writing known formulas of van-der-ZIL for full noise ideal diode [11].

In the case of reverse bias, satisfying the conditionwhen you can put, expressions (18) and (19) take the form

From formulas (25) and (26) it follows that in the range of frequencies that satisfy the condition of applicability of the stochastic boundary conditions, SPF diffusion current obratno.slishalp - nthe transition from the base of finite length in the case of ohmic, and in the case of a blocking contact to the database does not depend on frequency and is determined by the Schottky formula.

Calculate high-frequency limits of the additive components of the SPF diffusion current- nthe transition from the base of finite length, due to the random nature of the processes of thermal generation and recombination, for the case of ohmic and blocking contact to the base respectivelyand. In the case of small reverse bias, when the inequalityand in the case of zero and forward bias in the frequency range the final high-frequency limits of the additive components of the SPF diffusion current- nthe transition from the base of finite length, due to the random nature of the scattering processes, for the case of ohmic and blocking contact to the database doesn't exist:and.

While it is easy to show that when the displacement consideredand.

The final high-frequency limits of the additive components of the SPF diffusion current- nthe transition from the base of finite length, due to the random nature of the scattering, in the frequency rangefor the case of ohmic and blocking contact to the database exist only in the case of reverse bias, satisfying the conditionwhen you can putand are defined by the expression

Thus, at high frequencies the noise diffusion current is consideredp+- ntransition due to the random nature of the scattering processes, regardless of the applied voltage and when any structurep+- ntransition.

One of the possible ways to promote metabolism of body is of threshold characteristics of the infrared photodiodes based compositionx≃0.2 is to use the effect of suppressing the diffusion current inp - ntransitions with a short base and a blocking contact [1]. From formulas (25) and (26) shows that under reverse bias, satisfying the condition, SPF diffusion current under consideration- nthe transition from the short base is determined by the Schottky formula, i.e. in a wide frequency range, SPF diffusion current obratno.slishalp+- ntransition with a short base and a blocking contacttimes less SPF diffusion current is the same asp+- ntransition with a long base. However, from Fig. 2 and 4 shows that when a direct, zero and small reverse bias SPF diffusion currentp - ntransition with a short base and a blocking contacttimes less SPF diffusion current is the same asp - ntransition with a long base, only in a limited frequency range. Apparently, this is due to the fact that the kinetic diffusion length of holes decreases with increasing frequency and at high frequency becomes less than the thickness of the base. With such high frequencies SPF diffusion current is consideredp+- ntransition is determined by the random nature of the process is the scattering taking place in a narrow region near the interface OPZ - quasi-neutral regionntype, and does not depend on the type of contact (boundary conditions) at the point. Thus, to achieve high threshold characteristics of the infrared photodiodes basedcomposition x≃0.2 in the field of high frequencies due to the effect of noise suppression of the diffusion current inp - nthe transition from a short base and a blocking contact should be maintained atp - nthe transition of the reverse bias, satisfying the condition. Note that the results obtained do not correspond to the results of the calculations SPFp - ntransition with a short base [11], performed by methods of theory of random pulses. Apparently, this is due to the fact that the Langevin method used in the present work, allows you to properly take into account the stochastic boundary conditions of various types, while the methods of theory of random pulses, used in [11], do not allow it.

Calculate the low-frequency limits of expressions (18) and (19)

and:

(27)

(28)

and expressions(22) - (24):

,

,

:

(29)

thattab(30)

(31)

Put in expressions (27), (28) and (31)and calculate SPF diffusion current- ntransition with a short base for the case of ohmic and blocking contacts, as well as SPF diffusion current- ntransition with a long base. The results have the form

Comparing the obtained expression with differential impedance matchingp - ntransitions [1], it is easy to see that the results obtained are in accordance with the Nyquist theorem [11].

Literature

1. M.B. Reine, A.K. Sood, and Tredwell T.J. //Semiconductors and semimetals. New York: Academic Press, 1981. Vol. 18. Ch. 6.

2. Burlakov I.D., Selyakov A. Yu., V.P. Ponomarenko, Filachev A.M. // Proc. SPIE Vol. 7660, pp. 76603A1 - 76603A12.

3. Vilela M.F., S.F. Harris, R. E. Kvaas, Buell A.A., M.D. Newton, Olsson K.R., Lofgreen D.D., and Jonson S.M. // J. Electronic Materials, 2009, v. 38, No. 8, pp. 1755-1763.

4. Mynbayev CD, Ivanov-Omsk VI TEKHN. 2003, T. 37, vol. 10, S. 1153 - 1178.

5. Zi S.M. // Physics of semiconductor devices in 2 volumes, M: Peace. 1984, so 1 - 456 S., T. 2 - 455 S.

6. Semiconductor formation is spruce image signals. Under the editorship of Jaspers P., van de Ville, F., white, M., M.: Mir, 1979. Part II.

7. C.M. Van Vliet // Solid State Electronics. 1970, v. 13, No. 5, p. 649 - 657.

8. Neustroev, L.N., Osipov V.V. // FTP. 1981, T. 15, vol. 11, S. 2186-2196.

9. Shockley W. // Bell. Syst. Tech. J. 1949, v. 28, p. 435 - 489.

10. Rytov S.M. Introduction to statistical Radiophysics. Part I. stochastic processes. - M.: Nauka, 1976, S. 496.

11. Buckingham M Noise in electronic devices and systems. - M.: Mir. 1986, S. 399.

The way to reduce the spectral density of fluctuations of the diffusion current of the photodiode in the field of high frequencies, which consists in the fact that the p-n junction with a short base (d<L, where d is the thickness of the base, a L is the diffusion length of minority carriers in the base) and a blocking contact to the base serves reverse bias V satisfying the conditions
3kT<q|V|<Vb,tand 3kT<q|V|<Vb and,
where k is Boltzmann's constant;
T - temperature;
q is the electron charge;
Vb,t- voltage tunneling breakdown;
Vb,a- voltage avalanche breakdown.



 

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EFFECT: higher efficiency, broader functional capabilities.

3 cl, 3 tbl, 6 dwg

FIELD: fiber-optic communications, data protection, telecommunications, large-scale integrated circuit diagnosing and testing, single molecule spectrometry, astronomy, and medicine.

SUBSTANCE: proposed device has substrate carrying contact pads, One strip is made of superconductor in the form of meander and its ends are connected to contact pads. Other, additional, semiconductor strip is connected in parallel with above-mentioned strip made in the form of meander. Additional strip is made of superconductor whose kinetic inductance is lower than that of strip made in the form of meander.

EFFECT: enhanced speed, sensitivity, and bandwidth of detector.

9 cl, 2 dwg

FIELD: infrared detectors.

SUBSTANCE: proposed photodiode infrared detector has semiconductor substrate translucent for spectral photodetection region rays and semiconductor graded band-gap structure disposed on substrate;. graded band-gap structure has following layers disposed one on top of other on substrate end. Highly conductive layer of one polarity of conductivity and fixed forbidden gap width produced by heavy doping; layer of other polarity of conductivity and other forbidden gap width in the form of little hump whose value gradually rises from that corresponding to forbidden gap width of preceding layer and then, with smoother decrease to value corresponding to forbidden gap width of preceding layer or smaller. Working layer of same polarity of conductivity as that of preceding layer and fixed forbidden gap width equal to degree of final decrease in forbidden gap width of preceding layer and also equal to forbidden gap width in first of mentioned layer or smaller. Working layer is provided with p-n junction exposed at its surface. Layer disposed on working-layer p-n junction and having gradually increasing forbidden gap width to value corresponding to working layer and polarity of conductivity reverse to that of working layer.

EFFECT: maximized current-power sensitivity, enhanced maximal photodetection frequency, uniform parameters with respect to surface area.

12 cl, 2 dwg

FIELD: power engineering.

SUBSTANCE: invention is used in optical data acquisition systems with high registration efficiency of light radiation by means of avalanche photodiodes with Geiger discharge quenching circuit. Into solid Geiger detector with active restorer, which includes avalanche photodiode the anode whereof is connected to the shift voltage bus and cathode is connected to the first electrode of damping resistor, and a switching restoring transistor, there introduced is the additional damping resistor. The first electrode of the additional damping resistor is connected to the second electrode of damping resistor and to the sink of switching restoring transistor the gate of which is connected to the first electrode of damping resistor, and sink is connected to the second electrode of the additional damping resistor and detector power bus. Switching restoring transistor is made in the form of transistor with a built-in channel.

EFFECT: increasing dynamic range of detector as well as increasing registration efficiency.

1 dwg

FIELD: physics, photography.

SUBSTANCE: invention can be used, for instance in wide-field heat direction finding or thermal imaging devices working in two spectrum regions. The dual spectrum photodetector consists of p modules, each having photosensitive elements, two multiple-element photosensitive lines, a multiplexer and a base. The first multiple-element line is sensitive in one spectrum region and lies on the substrate of the first photosensitive element and the second multiple-element line is sensitive in the other spectrum region and lies on the substrate of the second photosensitive element. In one version first photosensitive elements are trapezium shaped, which enables to arrange the modules such that photosensitive structures, each formed by the lines which are sensitive in one spectrum region, have the shape of regular polygons. In the other version second photosensitive elements are rectangular shaped, which enables arrangement of the modules such that photosensitive structures are in form of a line.

EFFECT: design of dual spectrum large-format multiple-module photosensitive structures of different configurations.

8 cl, 6 dwg

FIELD: physics, semiconductors.

SUBSTANCE: invention relates to microelectronics and can be used in designing semiconductor ultraviolet radiation sensors. A semiconductor UV radiation sensor has a substrate on which there are series-arranged wiring layer made from TiN, a photosensitive AlN layer, and an electrode system which includes a platinum rectifying electrode which is semi-transparent in the C-region of UV radiation, connected to the AlN layer to form a Schottky contact, first and second leads for connecting to an external measuring circuit, where the first lead is connected to the wiring layer and the second to the rectifying electrode. The method of making a semiconductor UV radiation sensor involves successive deposition of a wiring TiN layer and a photosensitive AlN layer onto a substrate through reactive magnetron sputtering on a general processing unit in a nitrogen-containing gas medium with subsequent formation of a platinum rectifying electrode which is semitransparent in the C-region of UV radiation, connected to the photosensitive AlN layer to form a Schottky contact, and leads for connecting the rectifying electrode and the wiring layer to an external measuring circuit. The wiring and photosensitive layers are deposited continuously without allowing cooling down of the substrate. The platinum rectifying electrode is made through three-electrode ion-plasma sputtering of a platinum target at pressure of 0.5-0.6 Pa for 4-6 minutes, target potential of 0.45-0.55 kV and anode current of 0.8+1.2 A. Sensitivity of the end product is equal to 65-72 mA/W.

EFFECT: increased sensitivity of the end product.

2 cl, 2 dwg, 1 tbl

FIELD: physics.

SUBSTANCE: infrared radiation sensitive structure having a substrate whose top layer is made from CdTe, a 10 mcm thick working detector layer made from Hg1-xCdxTe, where x=xd=0.2-0.3, a 0.1-0.2 mcm thick insulating layer made from CdTe, and a top conducting layer with thickness of approximately 0.5 mcm also has a 0.5-6.0 mcm thick lower variband layer between the substrate and the detector layer, where the said variband layer is made from Hg1-xCdxTe, where the value of x gradually falls from a value in the range of 1-(xd+0.1) to a value xd, between the working detector layer and the insulating layer, a top variband layer with thickness of 0.03-1.00 mcm made from Hg1-xCdxTe where the value of x gradually increases from a value xd to a value in the range of 1-(xd+0.1), and dielectric layers between the insulating layer and the top conducting layer. Disclosed also is a method of making the said structure.

EFFECT: possibility of making a highly stable infrared sensitive structure with broad functional capabilities.

12 cl, 1 dwg

FIELD: physics.

SUBSTANCE: method of reducing spectral density of photodiode diffusion current fluctuation in high frequency range involves applying reverse bias V across a p-n junction with a short base and a blocking contact to the base, said reverse bias satisfying the conditions 3kT < q|V| < Vb,t and 3kt < q|V| < Vb,a, where: k is Boltzmann constant; T is temperature; q is electron charge; Vb,t is tunnel breakdown voltage; Vb,a is avalanche breakdown voltage.

EFFECT: disclosed method enables to increase the signal-to-noise ratio of the photodiode in the high frequency range by reducing spectral range of diffusion current fluctuation.

4 dwg

FIELD: physics.

SUBSTANCE: high signal-to-noise (S/N) ratio infrared photodiode has a heavily doped layer (1) of a main p-n junction, a heavily doped layer (2) of an additional p-n junction, a padded base (3) for the main and additional p-n junctions and a substrate (5). The common base (3) has a space-charge region (4) for the main p-n junction. An ohmic contact (6, 7, 8) is formed for each of the layers of the structure. The total thickness of the heavily doped layer of the main p-n junction and the space-charge region of the main p-n junction lying in the common base satisfies a condition defined by a mathematical expression. To increase the S/N ratio in the infrared photodiode, diffusion current of the additional p-n junction and the sum of the diffusion current and photocurrent of the main p-n junction are recorded, and the diffusion current of the additional p-n junction is then used for correlation processing of the signal and noise of the main p-n junction. S/N ratio in the infrared photodiode is increased by using diffusion current of the additional p-n junction, whose noise is correlated with noise of the diffusion current of the main (infrared radiation detecting) p-n junction, for correlation processing of the signal and noise of the main p-n junction.

EFFECT: high signal-to-noise ratio of the infrared photodiode.

2 cl, 2 dwg

FIELD: physics.

SUBSTANCE: inventions can be used in threshold photodetectors for detecting weak electromagnetic radiation in the infrared range. The high signal-to-noise ratio infrared photodiode has a heavily doped layer adjacent to a substrate which is transparent for infrared radiation, whose thickness l1 satisfies the condition: and a weakly doped layer of another conductivity type (base), whose thickness d satisfies the condition d<L. Ohmic contacts are formed along two opposite sides of the periphery of the weakly doped layer. To increase the signal-to-noise ratio in the infrared photodiode, the sum of diffusion current and photocurrent of the p-n junction, and current of the longitudinal conductance of the base, which flows between ohmic contacts formed along two opposite sides of the periphery of the weakly doped layer, is determined, while applying a small voltage across said contacts, which satisfies a given condition.

EFFECT: invention increases the signal-to-noise ratio of the infrared photodiode by using current of longitudinal conductance of the base, whose noise is correlated with noise of the diffusion current of the p-n junction, for correlated processing of the signal and the noise of the p-n junction which detects infrared radiation.

2 cl, 3 dwg

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