An Optimal Design Method for Inter-band Cascade Infrared Detectors

Abstract

The present invention provides an optimization design method for an inter-band cascade infrared detector, comprising the following steps: S1, by changing the absorption area A of the inter-band cascade detector and the thickness d of each absorption area m , generate a structural combination, and calculate the quantum efficiency QE of each structural combination; S2, the effect of the interface interdiffusion phenomenon of the inter-band cascade structure on carrier collection is equivalent to a potential barrier, and a dark current calculation model of the mid-infrared inter-band cascade detector is established to calculate the dark current value of the inter-band cascade detector of each structural combination; S3, calculate the corresponding equivalent noise power NEP, and construct a corresponding curve between the equivalent noise power NEP and the corresponding structural combination; S4, according to the NEP value of step S3, select the minimum NEP value, and determine the corresponding structural combination as the structure with the best detector performance. The present invention improves the calculation accuracy under reverse bias, fully considers the temperature conditions of the working environment, and performs corresponding performance adjustment and optimization.

Description

Technical Field

[0001] The invention belongs to the technical field of detector design, and in particular relates to an optimization design method for an inter-band cascade infrared detector. Background Art

[0002] The interband cascade infrared detector is a new type of semiconductor infrared detector. This type of detector combines the characteristics of barrier structure and multi-level absorption region. By connecting multiple short absorption regions in series, the carrier collection efficiency can be improved under the condition of short diffusion length. Dark current refers to the current in the detector under no light conditions, which is an important indicator for evaluating the performance of the detector. There is no need to intentionally dope the interband cascade structure to form a depletion region. Instead, the unidirectional transport of carriers is achieved through multi-quantum well relaxation and tunneling, which is significantly different from the traditional PN junction. The formula for calculating the dark current of the PN junction is no longer applicable. The dark current of the interband cascade infrared detector is mainly dominated by the diffusion current under high temperature conditions, such as 180 K to 300 K. As the temperature increases, the thermal motion of the carriers intensifies, resulting in an increase in the diffusion current, a decrease in the device signal-to-noise ratio, and an impact on the device detection performance. Different materials and their structural designs, such as the thickness and number of absorption regions, will affect the size of the dark current density and the carrier collection efficiency.

[0003] Antimonide-based type II superlattice materials have important applications in interband cascade infrared detectors. Ideally, the interface of the type II superlattice material structure should be perfect and abrupt, that is, the interface between the two materials should be clear and there should be no mutual penetration. However, in the actual preparation process, due to the segregation of In atoms and Sb atoms, the interfaces between different layers often undergo a certain degree of mutual diffusion, resulting in the actual thickness of the InAs layer being less than the designed thickness. The existence of this gradual interface causes the energy band of the interband cascade structure to shift, affecting the band structure and carrier collection.

[0004] At present, most methods for calculating the dark current of inter-band cascade infrared detectors directly use the dark current calculation formula proposed by Yang Ruiqing, which derives the thermal noise expression of the inter-band cascade detector and the average dark current formula in the inter-band cascade detector based on the balance principle of heat injection and collection current. Or some parameters such as minority carrier lifetime are extracted based on this formula and the dark current test results. In actual calculations, it is difficult to control the accuracy of the dark current estimation results due to complex factors such as measurement accuracy and the establishment of theoretical models.

[0005] Dark current is one of the key parameters for optimizing the performance of photodetectors. Improving the calculation accuracy of dark current can more accurately calculate other indicators, such as detection rate, equivalent noise power, etc. At the same time, the electrical parameters extracted based on a more accurate dark current model of inter-band cascade detectors will also be more accurate. Summary of the invention

[0006] The object of the present invention is to provide an optimization design method for an inter-band cascade infrared detector in view of the problems in the prior art.

[0007] To this end, the above-mentioned object of the present invention is achieved by the following technical solution: an optimization design method for an inter-band cascade infrared detector, characterized in that it comprises the following steps:

[0008] S1, based on a fixed step interval, by changing the absorption area A of the inter-band cascade detector and the thickness d of each absorption region m , generating a structural combination ( A ,d m ), calculate all structural combinations ( A ,d m ) is the quantum efficiency QE, where m represents the number of levels of the absorption zone;

[0009] S2, the effect of the inter-band cascade structure's interface interdiffusion on carrier collection is equivalent to a potential barrier, and a dark current calculation model for the inter-band cascade detector is established to calculate each structural combination ( A ,d m ) of the dark current :

[0010]

[0011] Where N is the total number of inter-band cascade structures, U is the total voltage, β m is the partial pressure coefficient of the mth absorption zone, T is the temperature, q is the electron charge, k is the Boltzmann constant, and n 0 is the minority carrier concentration, is the minority carrier lifetime, L e is the minority carrier diffusion length, represents the probability of the mth electron passing through the potential barrier, calculated as: ,in, The energy band difference is caused by the interfacial diffusion phenomenon;

[0012] S3, according to the structural combination calculated in step S1 and step S2 ( A ,d m ) quantum efficiency, dark current, calculate the corresponding equivalent noise power NEP, and construct the equivalent noise power NEP and the corresponding structure combination ( A ,d m ) is calculated as: , where h is Planck's constant, c is the speed of light in vacuum, To measure the bandwidth, λ is the operating wavelength;

[0013] S4, according to the NEP value calculated in step S3, select the structural combination corresponding to the minimum NEP value ( A ,d m ) is determined to be the structure with the best detector performance.

[0014] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0015] As a preferred technical solution of the present invention: in step S2, the inter-band cascade structure energy band diagram is drawn by the K·P model and the effective masses of electrons and holes are obtained. In the inter-band cascade structure energy band diagram, the energy band difference between the absorption region and the relaxation region caused by the gradual interface is calculated by analyzing the continuity and mutation of the energy band edge. ; The intrinsic carrier concentration is calculated by the effective mass of electrons and holes, as well as the bandgap width. The majority carrier concentration is calculated by the doping concentration and the intrinsic carrier concentration, and the minority carrier concentration is calculated using the intrinsic carrier concentration and the majority carrier concentration. The minority carrier lifetime is calculated through time-resolved photoluminescence spectrum experimental data. The diffusion length of minority carriers is calculated by measuring the quantum efficiency at different temperatures.

[0016] As a preferred technical solution of the present invention: in step S1, the thickness of the active region of the inter-band cascade structure is set to be the sum of the thicknesses of each level , where m refers to the mth absorption zone of the inter-band cascade structure, N refers to the total number of inter-band cascade structures, and the area is A, where d s The value range is 1µm -5µm, and the value range of A is 50×50µm 2 -200×200µm 2 .

[0017] As a preferred technical solution of the present invention: in step S1, the quantum efficiency QE is calculated as follows:

[0018]

[0019] in, is the mth level quantum efficiency, is the quantum efficiency of the mth order when light is incident from the substrate of the detector, is the quantum efficiency of the mth order when light is incident from the upper surface, calculated as follows:

[0020]

[0021] Where α is the absorption coefficient, d j is the thickness of the j-th absorption region, R is the reflectivity of the incident light to the substrate, and R s is the reflectivity of the incident light on the upper surface of the device after passing through the absorption region, is the quantum efficiency of a single stage when light is incident from the substrate, is the quantum efficiency of a single stage when light is incident from the top surface, calculated as follows:

[0022] Where d is the thickness of the single-stage absorption zone.

[0023] Compared with the prior art, the optimization design method of an inter-band cascade infrared detector of the present invention has the following beneficial effects: in the calculation of the dark current of the inter-band cascade infrared detector, a correction factor of the dark current formula is introduced, and the correction factor is the probability of electrons passing through the potential barrier. By describing the influence of the interface interdiffusion phenomenon on carrier collection, the calculation accuracy under small reverse bias is improved, and the problem that the dark current calculation results under small bias enter the saturation region too early compared with the experimental results before the correction term is added and the calculation results are too large is solved, and the influence of the potential barrier is gradually eliminated after the bias is increased. The present invention improves the accuracy of dark current calculation of the inter-band cascade infrared detector under the dominance of diffusion current based on minority carrier transport, provides more accurate data reference for the design of the structural parameters of the detector, and also provides a reliable basis for the performance optimization of the detector.

[0024] The optimization design method of the inter-band cascade infrared detector of the present invention significantly improves the dark current calculation accuracy under a small reverse bias, provides conditions for optimizing the performance of the detector under higher temperature working conditions, and further promotes the application of the inter-band cascade detector in the field of infrared imaging and spectral detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A comparison diagram of the calculation results and experimental data before and after adding the correction term in the dark current calculation of the present invention;

[0026] Figure 2 is the intrinsic carrier and electron concentration at different temperatures;

[0027] Figure 3a The dark current density test results and calculation results of 220K M1, M3, and M5;

[0028] Figure 3b These are the dark current density test results and calculation results of M1 220K, 200K, and 180K. DETAILED DESCRIPTION

[0029] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0030] An optimization design method for an inter-band cascade infrared detector comprises the following steps:

[0031] S1, based on a fixed step interval, by changing the absorption area A of the inter-band cascade detector and the thickness d of each absorption regionm , generating a structural combination ( A ,d m ), calculate all structural combinations ( A ,d m ) is the quantum efficiency QE, where m represents the number of levels of the absorption zone;

[0032] S2, the effect of the inter-band cascade structure's interface interdiffusion on carrier collection is equivalent to a potential barrier, and a dark current calculation model for the inter-band cascade detector is established to calculate each structural combination ( A ,d m ) of the dark current :

[0033]

[0034] Where N is the total number of inter-band cascade structures, U is the total voltage, β m is the partial pressure coefficient of the mth absorption zone, T is the temperature, q is the electron charge, k is the Boltzmann constant, and n 0 is the minority carrier concentration, is the minority carrier lifetime, L e is the minority carrier diffusion length, represents the probability of the mth electron passing through the potential barrier, calculated as: ,in, The energy band difference is caused by the interfacial diffusion phenomenon;

[0035] S3, according to the structural combination calculated in step S1 and step S2 ( A ,d m ) quantum efficiency, dark current, calculate the corresponding equivalent noise power NEP, and construct the equivalent noise power NEP and the corresponding structure combination ( A ,d m ) is calculated as: , where h is Planck's constant, c is the speed of light in vacuum, To measure the bandwidth, λ is the operating wavelength;

[0036] S4, according to the NEP value calculated in step S3, select the structural combination corresponding to the minimum NEP value ( A ,d m ) is determined to be the structure with the best detector performance.

[0037] In step S2, the inter-band cascade structure band diagram is drawn by the K·P model and the effective masses of electrons and holes are obtained. In the inter-band cascade structure band diagram, the band difference between the absorption region and the relaxation region caused by the gradual interface is calculated by analyzing the continuity and mutation of the band edge. ; The intrinsic carrier concentration is calculated by the effective mass of electrons and holes, as well as the bandgap width. The majority carrier concentration is calculated by the doping concentration and the intrinsic carrier concentration, and the minority carrier concentration is calculated using the intrinsic carrier concentration and the majority carrier concentration. The minority carrier lifetime is calculated through time-resolved photoluminescence spectrum experimental data. The diffusion length of minority carriers is calculated by measuring the quantum efficiency at different temperatures.

[0038] In step S1, the thickness of the active region of the inter-band cascade structure is set to be the sum of the thicknesses of each level. , where m refers to the mth absorption zone of the inter-band cascade structure, N refers to the total number of inter-band cascade structures, and the area is A, where d s The value range is 1µm -5µm, and the value range of A is 50×50µm 2 -200×200µm 2 .

[0039] In step S1, the quantum efficiency QE is calculated as follows:

[0040]

[0041] in, is the mth level quantum efficiency, is the quantum efficiency of the mth level when light is incident from the substrate, is the quantum efficiency of the mth order when light is incident from the upper surface, calculated as follows:

[0042]

[0043] Where α is the absorption coefficient, d j is the thickness of the j-th absorption region, R is the reflectivity of the incident light to the substrate, and R s is the reflectivity of the incident light on the upper surface of the device after passing through the absorption region, is the quantum efficiency of a single stage when light is incident from the upper surface, calculated as follows:

[0044] Where d is the thickness of the single-stage absorption zone.

[0045] In the prior art, a potential barrier refers to a blocking layer formed in a semiconductor due to a carrier concentration gradient. There is a potential energy difference on both sides of the layer, thereby forming a potential barrier.

[0046] There is a PN junction barrier formed by the space charge region in the PN junction. When a forward voltage is applied to the PN junction, the electric field in the barrier region weakens with the increase of the forward bias, the width of the barrier region narrows, the diffusion movement is strengthened, the drift movement is weakened, the PN junction is forward-conducted, and the junction resistance is very small; on the contrary, when a reverse voltage is applied to the PN junction, the electric field in the barrier region is enhanced, the barrier region becomes wider, the diffusion movement is weakened, and the drift movement is strengthened. At this time, the PN junction is in a reverse cut-off state, and the reverse resistance is very large.

[0047] The Schottky junction is a simple interface between a metal and a semiconductor. The work function of a semiconductor is generally smaller than that of a metal. Therefore, when a metal and a semiconductor (taking N-type as an example) come into contact, electrons flow from the semiconductor into the metal, forming a space charge region composed of positively charged, immovable impurity ions in the surface layer of the semiconductor. At the interface, the energy band of the semiconductor bends to form a high potential energy region, which is the Schottky barrier. Electrons must have an energy higher than this barrier to cross the barrier and flow into the metal. When balanced, the height of the Schottky barrier is the difference between the work functions of the metal and the semiconductor. When a reverse bias is applied, that is, a negative voltage is applied to the metal end relative to the semiconductor end, the barrier becomes wider, and it is difficult for electrons to flow from the semiconductor to the metal, so almost no current flows. This is because the reverse bias increases the height of the barrier, so that electrons need more energy to cross the barrier, resulting in a greatly reduced probability of electrons penetrating the barrier; when a forward bias is applied, that is, a positive voltage is applied to the metal end relative to the semiconductor end, the barrier becomes narrower, and it is easier for electrons to flow from the semiconductor to the metal, so the current can flow smoothly. If the work done by the electric field is exactly equal to the height of the potential barrier, then the effect of the potential barrier can be approximately ignored because the energy gained by the electrons is sufficient to overcome the barrier.

[0048] The nBn infrared detector is a semiconductor infrared detector with a novel structure. Its name comes from its typical three-layer structure: an n-type doped layer, a barrier layer, and another n-type doped layer. It is mainly used for medium-wave infrared (MWIR) or long-wave infrared (LWIR) detection, and has the characteristics of low dark current and high detection sensitivity. The design of the nBn detector utilizes the characteristics of the barrier. The barrier layer can realize the selective transmission of electrons / holes, effectively reduce the dark current passing through the device, especially the hot carrier current caused by minority carriers, thereby greatly reducing noise. At the same time, due to the absence of a high-field depletion region, the nBn detector will not affect the transmission of photocurrent.

[0049] It can be seen that by analyzing the electron transport characteristics under different bias conditions in detail, we can better understand the influence of potential barriers on electron movement and its importance in practical applications.

[0050] An optimization design method for an inter-band cascade infrared detector of the present invention comprises the following steps:

[0051] Establish a dark current calculation model for inter-band cascade detectors:

[0052] In the inter-band cascade structure, the electrons excited by heat in the absorption region scatter through the relaxation region through phonon resonance. In previous work, the present invention designed and tested a medium-wave inter-band cascade infrared detector based on InAs / GaAsSb superlattice. Ideally, the atomic components of each interface are not mixed, but through STEM microscopic atomic images, it is found that the actual component distribution is gradual at the interface. This is caused by the segregation of In and Sb. In atoms penetrate into the GaAsSb layer at the GaAsSb-InAs interface, causing Ga atoms to be exchanged into the InAs layer; As atoms are replaced by Sb atoms at the InAs-GaAsSb interface. It was finally observed that the actual InAs layer was thinner than the designed thickness. Unlike the ideal situation, in actual situations, the positions of the electron and hole energy levels are offset, resulting in the quantum well energy level in the relaxation region being slightly higher than the conduction band microband in the absorption region. The effect of energy level misalignment is similar to a potential barrier, resulting in a certain reverse bias required for carriers to be injected into the relaxation region. The response rate test experiment shows that when the reverse bias increases, the influence of the potential barrier is completely eliminated, that is, the probability of electrons passing through the potential barrier is related to the work done by the electric field. In each absorption region, the maximum value of the work done by the external bias U on the free electrons is , β m is the voltage factor for each absorption level. , that is, when the work done by the electric field is equal to the potential barrier height, the potential barrier effect can be considered to be almost eliminated. However, due to the tunneling effect of electrons, even if the energy provided by the external bias voltage is not enough to overcome the barrier, some electrons can still pass through the barrier to reach the relaxation zone. In order to better characterize the probability of electrons passing through the barrier, the present invention adopts the exponential function form used by the nBn structure detector to characterize this effect, that is, as the reverse bias increases, the probability of electrons passing through the barrier increases exponentially; when the reverse bias is large enough, the probability of electrons passing through the barrier is infinitely close to 1. Based on the dark current formula of the inter-band cascade detector proposed by Rui Q. Yang et al., a correction factor is added as shown in formula (1).

[0053] (1)

[0054] Where n 0 is the minority carrier concentration, is the minority carrier lifetime, L e is the minority carrier diffusion length, β m is the partial pressure coefficient of each absorption zone, U is the total voltage, T is the temperature, q is the electron charge, and k is the Boltzmann constant. is the probability of an electron passing through the potential barrier. When the reverse bias is very small, ≈0, electrons can hardly pass through the potential barrier; when the work done by the electric field is equal to the height of the potential barrier, ≈1, the potential barrier effect is approximately eliminated. Taking the 220K first-order absorption zone inter-band cascade detector as an example, the calculation results before and after adding the correction term are as follows Figure 1 Before the correction term is added, the dark current enters the saturation region too early under small bias voltage, and the calculated result is too large; after the correction term is added, the calculated result under small reverse bias voltage is more consistent with the experimental data, and the influence of the potential barrier is eliminated after the bias voltage is increased, which is in line with the expectations of the model establishment.

[0055] Model applicability analysis and electrical characteristic parameters:

[0056] In order to suppress the Auger recombination rate at high temperature, the doping concentration of the absorption region is designed to be However, a lower doping concentration will result in similar concentrations of electrons and holes at high temperatures. The carrier collection process will no longer be limited by minority carriers, but will be transformed into bipolar diffusion. The conditions derived from minority carrier transport in equation (1) will no longer hold. And equation (1) is a diffusion current calculation formula derived under the thermal noise limit, so the model is only applicable to dark current calculations dominated by diffusion current based on minority carrier transport.

[0057] Appropriate electrical parameters need to be used for dark current calculation and fitting. According to the K·P model calculation, the effective mass of electrons and holes in the InAs (2.85nm) / GaAsSb (2.10nm) superlattice material is The relationship between the bandgap width and temperature is: .

[0058] The intrinsic carrier concentration n i The calculation formula is:

[0059] (2)

[0060] Where h is Planck's constant, k is Boltzmann's constant, and T is temperature.

[0061] Hole concentration p 0 The calculation formula is:

[0062] (3)

[0063] Where N a is the doping concentration.

[0064] Electron concentration n 0 , hole concentration p 0 and the intrinsic carrier concentration n i The relationship is:

[0065] (4)

[0066] The electron concentration and intrinsic carrier concentration calculated from this are as follows: Figure 2When the temperature is higher than 220K, the majority and minority carrier concentrations do not meet the condition of a difference of one order of magnitude, and the carrier transport mechanism is transformed into bipolar diffusion.

[0067] The parameters used in the model are shown in Table 1. The minority carrier lifetime can be obtained by analyzing the time-resolved photoluminescence spectrum. Since there is no light incident when studying the dark current, the electric injection under reverse bias conditions is considered to be a small injection condition, and the minority carrier lifetime can be approximately considered to be the SRH lifetime. The diffusion length at different temperatures can be fitted through the experimental data of variable temperature quantum efficiency.

[0068] Table 1 Electrical characteristic parameters

[0069]

[0070] Detector structure design:

[0071] Device responsivity R:

[0072] (6)

[0073] l p is the average output current, p 0 is the average input power. p It can be expressed as:

[0074] (7)

[0075] Where q is the electron charge, η is the quantum efficiency at wavelength λ, h is Planck's constant, and c is the speed of light in vacuum. Combining equations (6) and (7), we can get:

[0076] (8)

[0077] The expression of detector equivalent noise power NEP is:

[0078] (9)

[0079] R I is the current response, is the mean square noise current. Assuming that only the current generated by shot noise is considered here, under reverse bias:

[0080] (10)

[0081] In the formula is the dark current, is the measured bandwidth. Combining the above formula, we can get:

[0082]

[0083] Based on the quantum efficiency calculation results and data such as the area of ​​the inter-band cascade detector and the thickness of each absorption zone, the minimum NEP value can be calculated to optimize the device structure design.

[0084] The dark current data of three groups of inter-band cascade detectors with different levels are calculated, and their structures are shown in Table 2. The total thickness of the absorption region of the three groups of devices is the same, namely, one level, three levels, and five levels, and the doping concentration is It is composed of a p-type InAs (2.85nm) / GaAsSb (2.10nm) type II superlattice, the tunneling region is composed of 5 GaAsSb (4.80nm) / AlAsSb (1.80nm) quantum wells, and the relaxation region is composed of 7 InAs (7.40 / 6.10 / 5.20 / 4.52 / 4.00 / 3.58 / 3.23nm) / AlAsSb (1.36nm).

[0085] Table 2 Device structure parameters

[0086]

[0087] Figure 3a The dashed line in the middle is the experimental data of dark current density of M1 at 220K, 200K, and 180K, and the solid line is the calculation result of the dark current model. Figure 3b In the figure, the dotted lines are the experimental data of dark current density of M1, M3 and M5 at 220K, and the solid lines are the calculation results of the dark current model. In addition to the diffusion current, the experimental data of dark current also include generation-recombination current, tunneling current, etc., but the mechanism of these currents in the inter-band cascade structure is still unclear. When the temperature rises, the thermal motion of carriers becomes more intense, and the proportion of diffusion current in the total dark current increases. The model calculation results and the experimental data have a high fitting accuracy, indicating that the model can better reflect the relationship between the dark current and temperature. Under the same temperature conditions, when the total thickness of the absorption region is the same, increasing the number of inter-band cascades can suppress the diffusion current, and the proportion of diffusion current in the total dark current decreases, and the error of the model calculation results increases. In addition, there may be tiny impurities or defects in the growth process of the three groups of device materials, and the superposition of preparation processes such as passivation layer deposition and etching may cause residual stress or damage, resulting in high dark current experimental data, affecting the fitting effect of the model.

[0088] The above-mentioned specific implementation methods are used to explain the present invention and are only preferred embodiments of the present invention, rather than limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. An optimization design method for an inter-band cascade infrared detector, characterized in that: The following steps are involved: S1, based on a fixed step interval, by changing the absorption area A of the inter-band cascade detector and the thickness d of each absorption region m , generating a structural combination ( A ,d m ), calculate all structural combinations ( A ,d m ) is the quantum efficiency QE, where m represents the number of levels of the absorption zone; S2, the effect of the inter-band cascade structure's interface interdiffusion on carrier collection is equivalent to a potential barrier, and a dark current calculation model for the inter-band cascade detector is established to calculate each structural combination ( A ,d m ) of the dark current : , where N is the total number of inter-band cascade structures, U is the total voltage, β m is the partial pressure coefficient of the mth absorption zone, T is the temperature, q is the electron charge, k is the Boltzmann constant, n0 is the minority carrier concentration, is the minority carrier lifetime, L e is the minority carrier diffusion length, represents the probability of the mth electron passing through the potential barrier, calculated as: ,in, The energy band difference is caused by the interfacial diffusion phenomenon; S3, according to the structural combination calculated in step S1 and step S2 ( A ,d m ) quantum efficiency, dark current, calculate the corresponding equivalent noise power NEP, and construct the equivalent noise power NEP and the corresponding structure combination ( A ,d m ) is calculated as: , where h is Planck's constant, c is the speed of light in vacuum, To measure the bandwidth, λ is the operating wavelength; S4, according to the NEP value calculated in step S3, select the structural combination corresponding to the minimum NEP value ( A ,d m ) is determined to be the structure with the best detector performance.

2. The optimization design method of an inter-band cascade infrared detector according to claim 1, characterized in that: In step S2, the inter-band cascade structure band diagram is drawn by the K·P model and the effective masses of electrons and holes are obtained. In the inter-band cascade structure band diagram, the band difference between the absorption region and the relaxation region caused by the gradual interface is calculated by analyzing the continuity and mutation of the band edge. ; The intrinsic carrier concentration is calculated by the effective mass of electrons and holes, as well as the bandgap width. The majority carrier concentration is calculated by the doping concentration and the intrinsic carrier concentration, and the minority carrier concentration is calculated using the intrinsic carrier concentration and the majority carrier concentration. The minority carrier lifetime is calculated through time-resolved photoluminescence spectrum experimental data. The diffusion length of minority carriers is calculated by measuring the quantum efficiency at different temperatures.

3. The optimization design method of an inter-band cascade infrared detector according to claim 1, characterized in that: In step S1, the thickness of the active region of the inter-band cascade structure is set to be the sum of the thicknesses of each level. , where d m is the thickness of the mth absorption zone, N is the total number of inter-band cascade structures, and the area is A, where d s The value range is 1µm -5µm, and the value range of A is 50×50µm 2 -200×200µm 2 .

4. The optimization design method of an inter-band cascade infrared detector according to claim 1, characterized in that: In step S1, the quantum efficiency QE is calculated as follows: ,in, is the mth level quantum efficiency, is the quantum efficiency of the mth order when light is incident from the substrate of the detector, is the quantum efficiency of the mth order when light is incident from the upper surface, calculated as follows: , where α is the absorption coefficient, d j is the thickness of the j-th absorption region, R is the reflectivity of the incident light to the substrate, and R s is the reflectivity of the incident light on the upper surface of the device after passing through the absorption region, is the quantum efficiency of a single stage when light is incident from the substrate, is the quantum efficiency of a single stage when light is incident from the top surface, calculated as follows: , where d is the thickness of the single-stage absorption zone.

Images