High signal-to-noise ratio infrared photodiode and method of increasing signal-to-noise ratio in infrared photodiode

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

 

The invention relates to photoelectronics and can be used in threshold photodetector devices for reception of weak electromagnetic radiation in the infrared (IR) range.

Known photosensitive semiconductor device (photodiode with low dark current (US patent 4242695) in order to reduce the diffusion current and the resulting noise photodiode formed an additional p-n junction having a common base with the main p-n junction.

The disadvantage of this semiconductor device is the necessity of forming an additional p-n junction, which significantly complicates the manufacturing process of a photosensitive semiconductor device, and the absence of ohmic contacts to the two opposite sides of the perimeter of the low-alloy layer (base) which, in turn, causes the inability to use, the current longitudinal conductivity base for correlated signal processing and noise of the main p-n junction.

In a known photodiode to increase the signal/noise reduce the diffusion current of the main p-n junction, since the reduction of the average value of the diffusion current will lead to a decrease of the spectral density of the noise.

The disadvantage of this method of increasing the signal to noise is that diffusion the output current of the additional p-n junction is not used for a correlated signal processing and noise of the main p-n junctions, that does not significantly increase the signal-to-noise in the photodiode.

The objective of the invention is to increase the signal/noise (S/N) IR photodiode through the use of current longitudinal (along the plane of the p-n junction) conductivity base, the noise which is correlated with the noise diffusion current of p-n junction, for correlated signal processing and noise p-n junction, recording infrared radiation.

The technical result is achieved by the fact that the IR-photodiode with a high signal-to-noise contains consistently located signalisierung layer adjacent to the transparent to infrared radiation substrate, whose thickness l1exceeds the length of the absorption of infrared radiation in the semiconductor and low-alloy layer of the other conductivity type (base), whose thickness d is less than the diffusion length of minority carriers. However, along the two opposite sides of the perimeter of the low-alloy layer formed ohmic contacts. Signalisierung layer, and each of the two ohmic contacts formed by low-alloy layer, connected to the chip. reading and processing the signal of a single indium column.

In the photodiode infrared radiation must be absorbed in signalground layer, so that the latter adheres to the substrate, and the thickness of selenology is consistent layer of l 1satisfies the condition:

,

where α is the absorption coefficient.

To improve the signal-to-noise in the IR photodiode register the sum of the diffusion current and the photocurrent p-n junction, and the current longitudinal conductivity of the base, which flows between the ohmic contacts formed along two opposite sides of the perimeter of the low-alloy layer. When this is served on one of the ohmic contacts to the low-alloy layer zero potential, ohmic contact to signalground layer potential corresponding to a small reverse bias on the p-n junction, on the other ohmic contact to the low-alloy layer potential, the sign of which is opposite to the sign of the potential for ohmic contact to signalground layer, and the value satisfies the condition

,

WHERE Q is the ELECTRON CHARGE,

ε0- electric constant,

ε is the dielectric permittivity of the semiconductor,

N2the concentration of dopant in the database

d is the thickness of the low-alloy layer,

VG- the voltage across the p-n junction,

Vbi- built-in diffusion potential of the p-n junction.

Then the current longitudinal conductivity of the base used for a correlated signal processing and noise p-n junction.

1 shows a photodiode with correli vannoy signal processing and noise, which can be used as a cell matrix IR sensor (top view).

Figure 2 shows a photodiode with correlated signal processing and noise (section a-a).

Figure 3 shows the photodiode with correlated signal processing and noise (section b-b).

Consider photodiode contains:

1 - signalisierung layer;

2 - low-alloy layer (base);

3 is transparent to infrared radiation substrate;

4 - indium column connected to the ohmic contact to signalground layer;

5, 6 - indium columns connected to ohmic contacts for low-alloy layer;

7 - passivating dielectric;

8 - metal layer.

Signalisierung layer 1 adjacent to transparent to infrared radiation substrate 3 and is designed to absorb infrared radiation. The thickness of the l1signalisierung layer 1 satises

,

where α is the absorption coefficient. Over signalground layer formed of low-alloy layer (base) 2. The thickness d of the low-alloy layer 2 satisfies the condition

d<L,

where L is the diffusion length of minority carriers in the base. To signalground layer 1 formed ohmic contact with the metal layer and the indium column 4 is connected to the readout circuit and signal processing. Along the jet, the x opposite sides of the perimeter of the low-alloy layer 2 is formed ohmic contacts, with the help of the metal layers and indium columns 5 and 6, respectively, connected to the readout circuit and signal processing.

Correlated signal processing and noise in the photodiode can be realized when the following two conditions.

First, the diffusion current of the p-n junction should be determined by the processes of thermal generation and recombination in the base 2. This condition is satisfied, if the concentration of dopant in the p-n junction 2 is substantially less than the concentration of dopant in signalground layer 1, i.e. when the inequality:

N2<<N

where N2the concentration of dopant in low-alloy layer 2,

N1the concentration of dopant in signalground layer 1.

Secondly, the recorded infrared radiation must be absorbed in signalground layer p-n junction 1, adjacent to the substrate. The second condition is met, if the thickness of signalisierung layer 1, satisfies the condition

,

where α is the absorption coefficient.

In the operating mode to one of the ohmic contacts to the low-alloy layer serves zero potential, and the ohmic contact to signalground layer serves a potential corresponding to a small reverse bias on the p-n junction. However, on the other the ohmic contact to the low-alloy layer serves potential the value which satisfies the conditionand the sign opposite to the sign of the potential for ohmic contact to signalground layer.

In the photodiode fluctuations diffusion current caused by fluctuations in the rate of thermal generation and recombination of electron-hole pairs in the weakly doped layer. Fluctuations of the longitudinal conductivity of the base is also caused by fluctuations in the rate of thermal generation and recombination of electron-hole pairs. Above it was noted that the thickness of the base of the proposed photodiode is less than the diffusion length. Therefore, fluctuations in the rate of thermal generation and recombination in any small part of the base of the photodiode will give the contribution to the noise diffusion current of p-n junction, and the noise current of the longitudinal conductivity of the base, which leads to correlation noise. Thus, in the illumination-side substrate of the proposed PD total current of the p-n junction will be the sum of the diffusion current and the photocurrent and noise diffusion current is correlated with the noise current of the longitudinal conductivity of the base.

From this it follows that the current longitudinal conductivity of the base, which flows between the ohmic contacts formed along two opposite sides of the low-alloy layer, can be used for correlated samples the signal processing and noise p-n junction, that will increase the signal-to-noise consider the IR photodiode. Thus, in the simplest case, the correlated signal processing and noise p-n junction is a multiplication of the current longitudinal conductivity base for normalizing factor

where µmin- the mobility of minority carriers in the base,

µmajthe basic mobility of charge carriers in the base,

τ is the lifetime of minority carriers in the base,

ni- own the carrier concentration in the semiconductor

A - area p-n junction,

l is the distance between the ohmic contacts to the low-alloy layer,

V is the voltage applied between the ohmic contacts to the low-alloy layer, and the subtraction of the normalized current longitudinal conductivity of the base from the sum of the diffusion current and the photocurrent of the main p-n junction.

1. IR-photodiode with a high signal-to-noise containing signalisierung layer and low-alloy layer of the other conductivity type (base), the thickness of which is less than the diffusion length of minority carriers, characterized in that along the two opposite sides of the perimeter of the low-alloy layer formed ohmic contacts, and signalisierung layer and each of the ohmic contacts to the opposite sides of the perimeter subregionalna what about the layer connected to the readout circuit and signal processing separate indium column, this signalisierung layer is located on the side of the substrate, transparent to infrared radiation, and its thickness satisfies the condition
,
where α is the absorption coefficient.

2. Method of improving the signal-to-noise in the IR photodiode containing signalisierung layer and low-alloy layer of the other conductivity type (base), namely, that register the amount of diffusion current and photocurrent of the p-n junction, and the current longitudinal conductivity of the base, which flows between the ohmic contacts formed along two opposite sides of the perimeter of the low-alloy layer, when applying for one of the ohmic contacts to the low-alloy layer zero potential, ohmic contact to signalground layer potential corresponding to a small reverse bias on the p-n junction, on the other ohmic contact to low-alloy layer potential, the sign of which is opposite to the sign of the potential for ohmic contact to signalground layer, and the value satisfies the condition

where q is the electron charge,
ε0- electric constant,
ε is the dielectric permittivity of the semiconductor,
N2the concentration of dopant in the database
d is the thickness of the low-alloy layer,
VG- the voltage across the p-n junction,
bi- built-in diffusion potential of the p-n junction,
then the current longitudinal conductivity of the base used for a correlated signal processing and noise p-n junction.



 

Same patents:

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.

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FIELD: physics.

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12 cl, 1 dwg

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2 cl, 2 dwg, 1 tbl

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1 dwg

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12 cl, 2 dwg

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3 cl, 3 tbl, 6 dwg

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EFFECT: higher efficiency, broader functional capabilities.

3 cl, 3 tbl, 6 dwg

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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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