Photodiode infrared detector

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

 

The invention relates to semiconductor technology and can be used to create photo-detectors (PSD) for the registration and measurement of infrared (IR) radiation in the form of a single photodiodes, and in the form of a matrix of photodiodes.

Known photodiode receiver IR-radiation (U.S. patent No. 4588446, IPC: 4 01L 21/385)containing transparent to radiation in the spectral region important aspect of the semiconductor substrate, the semiconductor graded gap structure located on the substrate, and graded gap structure made within a layer having a smooth increase of the band gap from the substrate to the surface, while the substrate is made of CdHgTe, and the specified layer obtained by reducing the surface leakage current diffusion annealing films of Cd or Zn.

Known photodiode receiver IR-radiation (U.S. patent No. 4549195, IPC: 4 01L 27/14)containing transparent to radiation in the spectral region important aspect of the semiconductor substrate, the semiconductor graded gap structure located on the substrate, and graded-gap structure is made up of two layers forming a p-n junction, made of materials having excellent from each other the width of the forbidden zone, the first layer located on the substrate and made of a material with a smaller bandgap, and the second layer of material is and the larger bandgap performed on the first layer, coating at the perimeter of the specified first layer and partially substrate, achieving reduction of surface leakage currents.

The closest technical solution is a photodiode receiver IR radiation (U.S. patent No. 5880510, IPC: 6 01L 31/00)containing transparent to radiation in the spectral region important aspect of the semiconductor substrate, the semiconductor graded gap structure located on the substrate, and the composition of the graded-gap structure was a layer of opposite conductivity type relative to the substrate and providing a reduced surface leakage currents passivating wide gap graded-gap layer, polozka, carry out the function of the working layer, and a layer of opposite conductivity type on a substrate made of CdHgTe, and passivating wide bandgap layer obtained by solution annealing films of Cd or Zn. Given the device is made in the form of a photodiode receiver IR-radiation matrix type.

The disadvantages of the above known technical solutions are: no maximum ampere-watt sensitivity, low frequency limit of the important aspect of the lack of homogeneity in the parameters area.

No maximum ampere-watt sensitivity related to the design features of the world is different photodetectors infrared radiation. Constructive solutions do not resolve the full extent of surface leakage currents and allow the presence of surface recombination of minority charge carriers, which results in insufficient high quantum yield and, as a consequence of lower ampere-watt sensitivity.

Low frequency limit of the important aspect is a consequence of the high series resistance in the layer of p-type, as in the high-frequency reception frequency limit photodiode receiver is determined not only by the time of the diffusion-drift of carriers through the base, by the time of their passage through the space charge region (SCR), and a value of RsC, where Rs- series resistance, including the resistance of spreading on the base layer and the contact resistance, the capacity of the p-n junction. It should be noted that in the case of heterodyne receiving a negative role Rseven more significant, because along with the frequency limit of a large value of Rsleads to a strong change of the operating point (bias voltage) of the p-n junction due to the large flow of the order of 1÷10 mA currents, whereas the typical power heterodyne reference beam can reach units of milliwatts.

The negative impact of large magnitude Rsis significant for low-frequency photodiode pickup the nicks matrix and column type. In the manufacture of such receivers technological approach to creating a basic contact instructs to do it in the shape of a frame surrounding matrix or line of photodiodes so that the series resistance is the sum of the spreading resistance in the base layer and has a value different for the Central and peripheral elements. The total current from a separate p-n junctions, the current in the base layer (from all elements or parts of elements of a matrix that is determined by the mode of operation of the multiplexer), can reach such a value that the voltage drop in the base layer due to them, shifts the operating point of the photosensitive elements. The latter is equivalent to increased photovoltaic connection between the elements and leads to an additional contribution to the noise FPU.

In the manufacture of a photodiode receiver IR radiation in the form of a matrix having a large value of Rsleads to heterogeneity parameters for square matrices, since this value is mandatory and includes the spreading resistance in the base layer, which is largest for Central and peripheral elements.

The technical result of the invention is:

- maximum ampere-watt sensitivity;

- increase the limit frequency of the important aspect;

- Costigan the e homogeneity of parameters across the square.

The technical result is achieved by the photodiode in the receiver of infrared radiation containing transparent to radiation in the spectral region important aspect of the semiconductor substrate, the semiconductor graded gap structure, placed on a substrate, the composition of the graded-gap structure has been executed by the substrate sequentially on each other: received strong doping of the highly conductive layer of one conductivity type with a fixed width of the forbidden zone; the layer of the other conductivity type by changing the width of the forbidden zone in the form of a "defect", with a gradual increase its value from the value corresponding to the width of the forbidden zone of the previous layer, and then a more gradual decline to a value corresponding to the width of the forbidden the area of the previous layer or less; working layer of the same conductivity type of that of the previous layer, with a fixed bandgap equal to the value of the end of the decay width of the forbidden zone in the previous layer and is equal to the width of the forbidden zone in the first of these layers or less, while in the working layer is the p-n junction extending to the surface; the layer located on the p-n junction of the active layer, with a gradual increase in the width of the forbidden zone from the value corresponding to the working layer, and the conductivity type of the faithful is opposite relative to the working layer.

In the photodiode of the receiver in the composition of the substrate is made of a buffer layer, which is graded gap structure.

In the photodiode of the receiver on the substrate in the composition of the graded gap structure made additional layer with gradually decreasing bandgap with increasing distance from the surface of the substrate of the same conductivity type as that of the received strong doping of the highly conductive layer.

Photodiode receiver is made in the form of a matrix.

In the photodiode receiver graded-gap semiconductor structure made of CdxHg1-xTe layer-by-layer variation of the bandgap width is set to layer-by-layer variation of composition.

In the photodiode receiver additional layer with gradually decreasing bandgap with increasing distance from the surface of the substrate is performed with variation of composition CdxHg1-xTe thickness from the corresponding x=0,37 from the substrate to the composition with x=0,222 at the border of the next layer, obtained a strong doping of the highly conductive layer with a fixed width of the forbidden zone is performed with a fixed composition CdxHg1-xTe thickness at x=0,222, layer by changing the width of the forbidden zone in the form of a "defect", with a gradual increase its value and then a more gradual decline performed with variation of composition CdxHg1-xTe thickness from the corresponding x=0,222 at the border of the previous layer to x=0.35 and, finally, to x=0,222 or up to x=0,19 near the border with the working layer, the working layer with a fixed bandgap performed with a fixed composition CdxHg1-xTe thickness with x=0,222 or x=0,19, the layer located on the p-n junction of the active layer, with a gradual increase in the width of the forbidden zone is performed with variation of composition CdxHg1-xTe in thickness from x=0,222 or x=0,19 at the interface and the working layer to x=0,47 on the surface of the graded-gap structure.

In the photodiode of the receiver substrate is made of GaAs.

In the photodiode of the receiver buffer layer is made transparent to radiation in the spectral range of sensitivity of the photodetector.

In the photodiode of the receiver buffer layer is made in the composition of the layers of CdTe and ZnTe.

In the photodiode receiver additional layer with gradually decreasing bandgap with increasing distance from the surface of the substrate is made of n-type with a dopant concentration of 3×1017cm-3received strong doping of the highly conductive layer is made of n-type dopant concentration n=order to show1×(10÷103) cm-3where the order to show1the concentration of dopant in the working layer, by changing the width of the forbidden zone in the form of a "defect" is made of p-type with a dopant concentration n=order to show1×(0,5÷2) cm-3where the order to show1 the concentration of dopant in the working layer, the working layer is made of p-type dopant concentration order to show1=5×1016cm-3while the n region of the active layer is made with a concentration of free charge carriers at the level of 1017÷1018cm-3layer with a gradual increase in the width of the forbidden zone is made of n-type dopant concentration is the same as in the working layer is p-type.

In the photodiode receiver additional layer with gradually decreasing bandgap with increasing distance from the surface of the substrate is made of a thickness of 0.5÷1.5 μm, obtained a strong doping of the highly conductive layer is made of a thickness of 0.5÷3 μm, layer by changing the width of the forbidden zone in the form of a "defect" is made with a thickness of 0.8÷2 μm, the working layer is made of a thickness of 8.2 μm, while the n region of the active layer is made of a thickness of 2÷2.5 μm, the layer with a gradual increase in the width of the forbidden zone is made a thickness of 0.1÷1.5 μm.

The invention is illustrated in the following description and the accompanying drawings. Figure 1 - changing the width of the forbidden zone with distance from the substrate surface graded-gap heteroepitaxial structure and layout layers, where 1 is the additional layer with a gradual decrease in the width of the forbidden zone, 2 - vysokotrave is ashy layer with a fixed width of the forbidden zone, 3 - layer with changing the width of the forbidden zone in the form of a "defect", 4 - working layer with a fixed width of the forbidden zone, a 5 - layer with a gradual increase in the width of the forbidden zone. Figure 2 - profile of the composition according to the thickness of the heteroepitaxial graded gap structure CdHgTe grown molecular-beam epitaxy on GaAs substrate.

It is known that in the manufacture of the IR photodiode receivers based on graded-gap structure, the presence of the highly conductive layer reduces series resistance Rs(Usarin, V.Vasiliev, Teachers, Chatvoice, Nay, Vinosum, Wmode, Ugedal, Aocakos. "Photodiodes with low series resistance based on graded-gap epitaxial layers CdxHg1-xThose". Optical journal, volume 66, No. 12, 1999, p.69-72). However, in the publication of the highly conductive layer is a region with a narrow gap structure CdHgTe, which leads to additional absorption of the detected radiation in a narrow-gap layer in the illumination side of the substrate, and has a negative impact on the ampere-watt sensitivity. In the present invention the reduction of the series resistance is due to the creation of signalisierung layer (2) n-type conductivity (see Figure 1), which is highly conductive. Such a decision device which replaces the problem of absorption of the radiation of the highly conductive layer with the width of the forbidden zone is not less than the working layer (4). In the case where the width of the forbidden zone of the highly conductive layer (2) coincides with the bandgap of the active layer (4), no absorption due to the effect of the moss-Burstein. With increasing width of the forbidden zone vysokoprohodimoy layer (2) absorption effect disappears.

In the latter case, an additional positive effect is the achievement of the cut-off radiation in the shortwave part of the spectrum of cold cut filter, this role is performed by the highly conductive layer (2) with a bandgap greater than that of the worker (4) of the layer.

Thus, having received strong doping of the highly conductive layer causes the increase of the limit frequency of the important aspect of achieving uniformity parameters area, in particular in the manufacture of the infrared photodiode receiver in the form of a matrix by reducing the series resistance in the working p-layer.

On the other hand, the maximum ampere-watt sensitivity of the proposed device is implemented also due to the presence of layers (3) and (5) (see Figure 1). Layer (5) with a gradual increase in the width of the forbidden zone eliminates the effect of surface recombination of minority carriers and suppress surface leakage currents, and the layer (3) by changing the width of the forbidden zone in the form of a "defect" bar minor wear who ate charge in the working layer (4). As a result of this bilateral effect on minority charge carriers, aimed at ensuring their participation in the formation of a signal at the important aspect, provides a higher quantum yield and, consequently, increases the ampere-watt sensitivity.

The width of the forbidden zone in the working layer (4) may vary within wide limits, depending on the technical requirements to parameters of a sensor to detect radiation from a remote object.

The magnitude and profile of the width of the forbidden zone in the graded-gap layer structure is determined for each specific case (the width of the gap of the active layer, the temperature of the photodetector, the physical parameters of the semiconductor) of the accounting requirements of suppression of recombination of minority carriers and the maximum quantum efficiency.

Photodiode receiver of infrared radiation includes a semiconductor substrate and made her graded-gap semiconductor structure, which in General consists of arranged on the substrate sequentially: the highly conductive layer, a layer with a change in the width of the forbidden zone in the form of a "defect", the working layer from the p-n junction, a layer with a gradual increase in the width of the forbidden zone.

Semiconductor substrate, for example, of GaAs is transparent to infrared radiation in the area is the sensitivity of the photodetector. In the composition of the substrate, if necessary, executed a buffer layer including layers of CdTe and ZnTe. This bologny the buffer is used for exact matching lattices of the substrate material and the material layers of graded-gap structure, performing an active function in the important aspect. Buffer as the substrate is transparent in the spectral range of important aspect.

Graded-gap semiconductor structure is made on the basis of CdHgTe, for example, with the structure shown in figure 2.

On the substrate or the buffer layer of the substrate, when it is present in the composition of the graded-gap semiconductor structures formed (Fig 1) additional layer (1) with a gradual decrease in the width of the forbidden zone. The layer is designed to eliminate the effect of interface phenomena at the interface of the substrate - graded gap structure on the formation of a signal at the important aspect and is performed as necessary. In particular in figure 2, are given as examples of the implementation of graded-gap structure, this layer is absent. He is a graded-gap layer of p - or n-type with bandgap Eg, smoothly changing from Eg1to Eg2(Eg1>Eg2) and a thickness of 0.5 to 1.5 μm. When this variation of the bandgap width is set by variation of the composition in thickness. In particular, the layer is formed so that the composition CdxHg1-xTe this layer connecting to the changes from the x=0.37 to composition with x=0,222, at a thickness of 1.2 μm and alloyed indium concentration n=3×1017cm-3.

On the additional layer (1), if it is present in graded gap structure, or on the substrate is highly conductive layer constituting the layer (2) with a fixed width of forbidden zone (Figure 1). He made signalground, n-type conductivity, with Eg=Eg2thickness from 0.5 to 3.0 μm, a concentration of n=order to show1×(10÷103) cm-3where the order to show1the concentration of dopant in the working layer (4). Fixed the width of the gap is due to a fixed structure thickness. In particular, the layer (2) formed with a constant composition CdxHg1-xTe with x=0,222, of a thickness of 2.7 μm and alloyed indium concentration n=3×1017cm-3.

On the highly conductive layer (2) is a layer (3) by changing the width of the forbidden zone in the form of a "defect", a different type conductivity, p-type, with a gradual increase in the width of the forbidden zone from Eg2to Eg3and then a more gradual decline to Eg4thickness from 0.8 to 2.0 μm, the concentration of p=order to show1×(0,5÷2) cm-3where the order to show1the concentration of dopant in the working layer (4). When this variation of the bandgap width is set by variation of the composition in thickness. In particular, when EC2=EC4layer is formed so that the composition CdxH 1-xTe this layer gradually changes from the corresponding x=0,222 up to x=0.35 and then more gradually changes to the composition with x=0,222, at a thickness of 1 μm and the concentration of p=6×l015cm-3. When EC2>Eg4composition CdxHg1-xTe this layer gradually changes from the corresponding x=0,222 up to x=0.35 and then more gradually changes to the composition with x=0,19. The latter corresponds to the longer-wavelength region of the important aspect. The conductivity type of the layer is a vacancy or obtained by doping As.

Layers (1)to(3) are transparent to IR radiation in the region of the important aspect.

Working layer (4) p-type conductivity formed on the layer (3) (see Figure 1) with a fixed bandgap equal to the value of the end of the decay width of the forbidden band Eg4in the layer (3) and is equal to the value of the band gap Eg2in the highly conductive layer (2) or less than the width of the forbidden band Eg2in the highly conductive layer (2). While in the working layer (4) created a p-n junction extending to the surface. The photodiode is formed by doping the surface, forming a region with a conductivity type opposite to the conductivity type of the active layer (4). The depth of the region of n-type conductivity in the working layer (4) is from 2 to 2.5 μm, the concentration of free charge carriers at the level of 1017÷1018cm-3. Pointed to by the second region is formed by doping indium or doped by ion implantation of boron.

The thickness of the working layer is determined by the desired parameters of a photodiode receiver and may be, for example, of 8.2 μm. The concentration of dopant in the working layer (4) is order to show1=5×1016cm-3. Fixed the width of the gap is due to a fixed structure thickness. In particular, the working layer (4) formed with a constant composition CdxHg1-xTe with x=0,222 that corresponds Eg4=EC2or with constant composition CdxHg1-xTe with x=0,19, which corresponds to Eg4<Eg2.

On the surface region of n-type conductivity in the working layer (4) is a layer (5) with a gradual increase in the width of the forbidden zone on the value of Eg4to the value of Eg5and type conductivity, opposite to the working layer, that is n-type. Its thickness ranges from 0.1 to 1.5 μm. When this variation of the bandgap width is set by variation of the composition in thickness. In particular, the layer is formed so that the composition CdxHg1-xTe this layer gradually changes from the corresponding x=0,222 or x=0,19 up to composition with x=0,47 on the surface. The concentration of free carriers is the same as in the region of n-type conductivity of the active layer (4) with the same means to achieve it.

Offer photodiode receiver IR radiation is characterized by a series resistance Rs=8 On the quantum efficiency at the maximum sensitivity η =0,7, which corresponds to theoretical value for the unenlightened surface CdHgTe.

In the case of execution of a photodiode receiver IR radiation in the form of matrix, a small value of Rsprovides a uniform voltage offset all of the photodiodes, asked the silicon multiplexer.

Photodiode receiver IR radiation works as follows.

The flow of infrared radiation passes through the substrate layers (1)to(3), is not absorbed by them, and gets into the working layer (4) (Figure 1). In the working layer (4) is absorbed past the infrared radiation and generation of minority carriers, which are tightened to the p-n transition, captured them and generate a photocurrent that form the signal of the important aspect. This pramosone p-n junction formed by layers (2) and (3), has a low differential resistance.

1. Photodiode receiver infrared radiation containing transparent to radiation in the spectral region important aspect of the semiconductor substrate, the semiconductor graded gap structure, placed on a substrate, characterized in that the composition of the graded-gap structure has been executed by the substrate sequentially on each other: received strong doping of the highly conductive layer of one conductivity type with a fixed width of the forbidden zone, a layer of a different conductivity type from what emeniem width of the forbidden zone in the form of a "defect", with a gradual increase its value from the value corresponding to the width of the forbidden zone of the previous layer, and then a more gradual decline to a value corresponding to the width of the forbidden zone of the previous layer or less; working layer of the same conductivity type of that of the previous layer, with a fixed bandgap equal to the value of the end of the decay width of the forbidden zone in the previous layer and is equal to the width of the forbidden zone in the first of these layers or less, while in the working layer is the p-n junction extending to the surface; the layer located on the p-n junction working layer, with a gradual increase in the width of the forbidden zone from the value corresponding to the working layer, and the conductivity type opposite to the working layer.

2. Photodiode receiver according to claim 1, characterized in that the substrate is made of a buffer layer, which is graded gap structure.

3. Photodiode receiver according to claim 1, characterized in that on the substrate in the composition of the graded gap structure made additional layer with gradually decreasing bandgap with increasing distance from the surface of the substrate of the same conductivity type as that of the received strong doping of the highly conductive layer.

4. Photodiode receiver according to claim 2, characterized in that on the substrate in the Ostrava graded gap structure made additional layer with gradually decreasing bandgap with increasing distance from the surface of the substrate, the same type of conductivity as that of the received strong doping of the highly conductive layer.

5. Photodiode receiver according to claim 1, characterized in that it is made in the form of a matrix.

6. Photodiode receiver according to claim 1, wherein the graded-gap semiconductor structure made of CdxHg1-xTe layer-by-layer variation of the bandgap width is set to layer-by-layer variation of composition.

7. Photodiode receiver according to claim 3 or 4, characterized in that the additional layer with gradually decreasing bandgap with increasing distance from the surface of the substrate is performed with variation of composition CdxHg1-xTe thickness from the corresponding x=0,37 from the substrate to the composition with x=0,222 at the border of the next layer, obtained a strong doping of the highly conductive layer with a fixed width of the forbidden zone is performed with a fixed composition CdxHg1-xTe thickness at x=0,222, layer by changing the width of the forbidden zone in the form of a "defect", with a gradual increase its value and then a more gradual decline, performed with variation of composition CdxHg1-xTe thickness from the corresponding x=0,222 at the border of the previous layer to x=0.35 and, finally, to x=0,222 or up to x=0,19 near the border with the working layer, the working layer with a fixed bandgap performed with a fixed composition CdxHg1-xTe thickness is not with x=0,222 or x=0,19, layer located on the p-n junction of the active layer, with a gradual increase in the width of the forbidden zone is performed with variation of composition CdxHg1-xTe in thickness from x=0,222 or x=0,19 at the interface and the working layer to x=0,47 on the surface of the graded-gap structure.

8. Photodiode receiver according to claim 1, characterized in that the substrate is made of GaAs.

9. Photodiode receiver according to claim 2, characterized in that the buffer layer is made transparent to radiation in the spectral range of sensitivity of the photodetector.

10. Photodiode receiver according to claim 2 or 9, characterized in that the buffer layer is made in the composition of the layers of CdTe and ZnTe.

11. Photodiode receiver according to claim 3 or 4, characterized in that the additional layer with gradually decreasing bandgap with increasing distance from the surface of the substrate is made of n-type dopant concentration 3·1017cm-3received strong doping of the highly conductive layer is made of n-type dopant concentration n=order to show1·(10÷103) cm-3where the order to show1the concentration of dopant in the working layer, by changing the width of the forbidden zone in the form of a "defect" is made of p-type dopant concentration n=order to show1·(0,5÷2) cm-3where the order to show1the concentration of dopant in the working layer, the working layer in the complete p-type dopant concentration order to show 1=5·l016cm-3while the n region of the active layer is made with a concentration of free charge carriers at the level of 1017÷1018cm-3layer with a gradual increase in the width of the forbidden zone is made of n-type dopant concentration is the same as in the working layer is p-type.

12. Photodiode receiver according to claim 3 or 4, characterized in that the additional layer with gradually decreasing bandgap with increasing distance from the surface of the substrate is made of a thickness of 0.5÷1.5 μm, obtained a strong doping of the highly conductive layer is made of a thickness of 0.5÷3 μm, layer by changing the width of the forbidden zone in the form of a "defect" is made with a thickness of 0.8÷2 μm, the working layer is made of a thickness of 8.2 μm, while the n region of the active layer is made of a thickness of 2÷2.5 μm, the layer with a gradual increase in the width forbidden zone is made a thickness of 0.1÷1.5 μm.



 

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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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