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

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

 

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 4,242,695), in order to reduce the diffusion current and the resulting noise photodiode formed an additional p-n junction located at the side of the substrate, at a distance smaller than the diffusion length of minority carriers in the base from the main one.

The disadvantage of this semiconductor device is the absence of ohmic contact to the p region of the additional p-n junction, which excludes the possibility of using diffusion current additional p-n junction 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 do not use the correlation noise diffusion currents of the main and additional p-n junctions that do not significantly increase the ratio of the signal is noise in the photodiode.

The objective of the invention is to increase the signal/noise (S/N) IR photodiode through the use of diffusion current additional p-n junction, the noise which is correlated with the noise diffusion current main (recording IR radiation) of the p-n junction, the correlated signal processing and noise of the main p-n junction.

The technical result is achieved by the fact that the IR photodiode with a high signal-to-noise contains signalisierung layer of the basic p-n junction, signalisierung additional layer p-n junction, as well as the General base of the basic and additional p-n junctions, the thickness of which is less than the diffusion length of minority carriers in the common database. Each consecutive layer signalisierung layer of the basic p-n junction, the overall framework of the basic and additional p-n junctions, and signalisierung additional layer p-n p-n junction is connected to the readout circuit and signal processing separate indium column. This signalisierung layer of the basic p-n junction, registering IR radiation, is located on the side of the substrate, and the sum of the thicknesses signalisierung layer of the main p-n junction and the space charge region of the main p-n junction located in the common database, satisfies the condition:

where

the thickness of the space charge region of the main p-n junction;

ε is the dielectric permittivity,

ε0- electric constant,

q is the electron charge,

Nbthe concentration of dopant in the common database,

Eg- the width of the forbidden zone,

- thickness signalisierung layer of the main p-n junction,

α is the absorption coefficient.

To improve the signal-to-noise in the IR photodiode containing signalisierung layer of the basic p-n junction, signalisierung additional layer p-n junction, as well as the General base of the basic and additional p-n junctions, record the sum of the diffusion current and the photocurrent of the main p-n junction, and the diffusion current additional p-n junction. Then the diffusion current additional p-n junction is used for a correlated signal processing and noise of the main p-n junction.

1 shows a photodiode with correlated signal processing and noise, which can be used as a cell matrix IR sensor.

Figure 2 shows a photodiode (top view).

Consider photodiode contains:

1 - signalisierung layer of the basic p-n junction;

2 - signalisierung additional layer p-n junction;

3 - the General database of primary and secondary p-n junctions;

4 - an area about transtorno charge of the main p-n junction, located in the common database;

5 - a substrate;

6 - indium column connected to the ohmic contact to signalground layer of the main p-n junction;

7 - indium column connected to the ohmic contact to the common base and additional p-n junctions;

8 - indium column connected to the ohmic contact to signalground additional layer p-n junction;

9 - passivating dielectric;

10 - metal layer.

Signalisierung layer 1 of the main p-n junction formed by the substrate 5 and is intended for registration of IR radiation. Between signalground layer 2 additional p-n junction and signalground layer 1 of the main p-n junction is a common base 3 of the main and additional p-n junctions. The total thickness d of the base 3 satises d<L, where L is the diffusion length of minority carriers in the common database. Area 4 space charge of the main p-n junction is located in the common database 3. Signalisierung layer 1 of the main p-n junction is connected by ohmic contact, the metal layer and indium column 6 with the readout circuit and signal processing. General base 3 of the main and additional p-n junctions are connected via an ohmic contact metal layer and the indium column 7 with the readout circuit and signal processing Signalisierung layer 2 additional p-n junction is connected through an ohmic contact, and indium column 8 with the readout circuit and signal processing, i.e. for each layer patterns formed ohmic contact.

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

First, the diffusion current of the main and additional p-n junctions should be determined by the processes of thermal generation and recombination in the common database.

This condition is satisfied, if the concentration of dopant in the common database of the main and additional p-n junctions is substantially less than the concentration of dopant in signalisierung the layers adjacent to the common database, i.e. when the following inequalities:

Nb<<N1and Nb<<N2,

where Nbthe concentration of dopant in the common database of the main and additional p-n junctions,

N1the concentration of dopant in signalground layer of the main p-n junction adjacent to the substrate,

N2the concentration of dopant in signalground additional layer p-n junction.

Secondly, the recorded IR radiation must be absorbed in signalground layer 1 of the main p-n junction adjacent to the substrate, and 4 space charge of the main p-n junction.

The second condition is met if the sum of the thicknesses of the area 4 space charge of the main p-n adapter is Yes and signalisierung layer 1 of the main p-n junction, adjacent to the substrate that satisfies the condition

where

the thickness of the space charge region of the main p-n junction;

ε is the dielectric permittivity,

ε0- electric constant,

q is the electron charge,

Nbthe concentration of dopant in the common database,

Eg- the width of the forbidden zone,

- thickness signalisierung layer of the main p-n junction,

α is the absorption coefficient.

As mentioned above, the main and additional p-n junctions have a common base, the thickness of which is less than the diffusion length. Therefore, in the case when the primary and secondary p-n junctions filed a reverse bias, part thermogenerators in any small region of the base charge carriers can diffuse to the main p-n junction, and some additional, which leads to correlation noise diffusion current of the main and additional p-n junctions. Thus, in the illumination from the substrate under consideration photodiode on the main and additional p-n junctions, which filed a reverse bias current of the main p-n junction will be the sum of the diffusion current and the photocurrent and current additional p-n junction diffusion current, the noise which is correlated with the noise diff is precise current main p-n junction.

From this it follows that the diffusion current additional p-n junction can be used for a correlated signal processing and noise of the main p-n junction, which will increase the signal-to-noise ratio of the considered IR photodiode. Thus, in the simplest case, the correlated signal processing and noise of the main p-n junction is a subtraction of the diffusion current additional p-n junction 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 of the basic p-n junction, signalisierung additional layer p-n junction, as well as the General base of the basic and additional p-n junctions, the thickness of which is less than the diffusion length of minority carriers in the common database, wherein each of the consecutive layers - signalisierung layer of the basic p-n junction, the overall framework of the basic and additional p-n junctions, and signalisierung additional layer p-n junction is connected to the readout circuit and signal processing separate indium column, while signalisierung layer of the basic p-n junction, registering IR radiation, is located on the side of the substrate, and the sum of the thicknesses signalisierung layer of the main p-n junction and the field of spatial ZAR is Yes main p-n junction, located in the common database that satisfies the condition
where
the thickness of the space charge region of the main p-n junction;
ε is the dielectric permittivity,
ε0- electric constant,
q is the electron charge,
Nbthe concentration of dopant in the common database,
Eg- the width of the forbidden zone,
- thickness signalisierung layer of the main p-n junction,
α is the absorption coefficient.

2. Method of improving the signal-to-noise in the IR photodiode containing signalisierung layer of the basic p-n junction, signalisierung additional layer p-n junction, as well as the General base of the basic and additional p-n junctions, namely, that register the amount of diffusion current and photocurrent of the main p-n junction, and the diffusion current additional p-n junction, and then the diffusion current additional p-n junction is used for a correlated signal processing and noise of the main p-n junction.



 

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FIELD: physics.

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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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