Hg1-xCdxTe光导探测器的电学参量分析

测量了Hg     

Hg1—xCdxTe禁带宽度附近折射率增强效应

用红外椭圆偏振光谱测量了室温下Hg1-xCdxTe(x=0.276,0.309,0.378)体材料位于禁带宽度之下、附近和之上的折射率。对每一种组份样品均观察到明显的折射率增强效应。折射率峰值所对应的能量位置近似等于其带宽度。禁带宽度之上折射率皮长λ变化可用Sellmeier色散关系n^2(λ)=a1 a2/λ^2 a3/λ^4 a4/λ^6进行拟合。     

Temperature dependence of 1/f noise in Hg1-xCdxTe MIS infrared detectors

We measured 1/f noise on Hg_0.71Cd_0.29Te Metal-Insulator-Semiconductor (MIS) infrared detectors operated over the temperature range of 40 K to 90 K under 300 K Infrared (IR) radiation. The purpose of the study was to identify the sources of 1/f noise, especially in relation to the dark current. The devices were operated in the correlated double sampling mode where the voltage across the MIS capacitor was sampled at empty potential well and right after the accumulation of minority carriers in the well due to IR radiation generation. The noise power spectral density for the charge integrated in the MIS well was investigated in relation to the dominant component of dark current. At lower temperatures T⩽65 K, the charge noise power spectral density was found to depend quadratically on the dark current. At higher temperatures, this quadratic dependence did not exist. We attribute the dark current to a mixture of tunneling and depletion-region-originated minority carrier generation which seems to be responsible for 1/f fluctuations in these structures for temperatures below 65 K     

Heterojunction blocking contacts in MOCVD grown Hg1-xCdxTe long wavelength infrared photoconductors

The theoretical and experimental performance of Hg_1-xCd _xTe long wavelength infrared (LWIR) photoconductors fabricated on two-layer heterostructures grown by in situ MOCVD has been studied. It is shown that heterojunction blocking contact (HBC) photoconductors, consisting of wider bandgap Hg_1-xCd_x Te on an LWIR absorbing layer, give improved responsivity, particularly at higher applied bias, when compared with two-layer photoconductors incorporating n⁺/n contacts. An extension to existing device models is presented, which takes into account the recombination rate at the heterointerface and separates it from that occurring at both the contact-metal/semiconductor and passivant/semiconductor interfaces. The model requires a numerical solution to the continuity equation, and allows the device responsivity to be calculated as a function of applied electric field. Model predictions indicate that a change in bandgap across the heterointerface corresponding to a compositional change of Δx⩾0.04 essentially eliminates the onset of responsivity saturation due to minority carrier sweepout at high applied bias. Experimental results are presented for frontside-illuminated n-type Hg_1-xCd_xTe photoconductive detectors with either n⁺/n contacts or heterojunction blocking contacts. The devices are fabricated on a two-layer in situ grown MOCVD Hg_1-xCd_xTe wafer with a capping layer of x=0.31 and an LWIR absorbing layer of x=0.22. The experimental data clearly demonstrates the difficulty of forming n ⁺/n blocking contacts on LWIR material, and indicates that heterojunctions are the only viable technology for forming effective blocking contacts to narrow bandgap semiconductors     

Analysis of Hg1-xCdxSe alloys inelectroreflectance

An electrolyte electroreflectance study on Hg_1-xCd_xSe alloy films is first reported. The critical point energies E₀ and E₁ are obtained for different CdSe composition samples and material homogeneities are also discussed     

The Auger-effect in Hg1−xCdxTe

The temperature dependence of the Auger-lifetime of n-Hg_1−xCd_xTe is investigated both theoretically and experimentally for several values of bandgap and of extrinsic carrier-concentration n_ex in the whole range between room and He-temperatures. For semiconducting compounds a pronounced minimum of the lifetime between 10 and 50K and an exponential increase at still lower temperatures are found. The position of the minimum and the exponent depend mainly on the value of the bandgap and on the ratio of the conduction- and valenceband effective masses. Apart from the extended temperature range, which does not allow the use of classical statistics, our calculation differs from earlier work in so far, as we take the band energies and the overlap integrals of conduction- and valenceband Bloch-functions from a k·p-calculation. For semiconducting compounds, we compare the results with those obtained from an estimate of the overlap integrals given by Antončik and Landsberg. Whereas both results are compatible at high temperatures, characteristic differences occur at low temperatures, where we find the lifetime to be proportional to rather than to n_ex⁻². For semimetallic compounds we calculate a weakly temperature dependent Auger-time of the order of 0.1–1 nsec.     

Hg1?x?y?zCdxMnyZnzTe: A new alternative to Hg1?xCdxTe

The results of studying the most important energy-band parameters of a new quinary semiconductor HgCdMnZnTe solid solution are reported. It is shown that the parameters of HgCdMnZnTe can make this material highly competitive with HgCdTe, which is the main material for infrared photoelectronics in the spectral ranges 3–5 and 8–14 μm. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 38, No. 12, 2004, pp. 1414–1418. Original Russian Text Copyright ? 2004 by Gorbatyuk, Markov, Ostapov, Rarenko.     

Dark current characteristics of GaAs metal-semiconductor-metal(MSM) photodetectors

Calculations of the electron and hole components of dark current in a GaAs metal-semiconductor-metal (MSM) photodetector are presented. A quantum-mechanical model for the electron and hole transport behavior in the contact regions which is used to determine dark current as a function of electric field is developed. The model reduces to a conventional thermionic emission model if an ideal barrier transmission coefficient is assumed. In order to assess the accuracy of the model, photodetectors have been fabricated and tested. Theoretical calculations and experimental data are compared, and good agreement is obtained. Possible modifications to enhance the usefulness of the model are discussed     

Current transport in metal-semiconductor-metal (MSM) structures

The current-voltage characteristics of a metal-semiconductor-metal structure (essentially two metal-semiconductor contacts connected back to back) have been studied based on the thermionic emission theory. When a uniformly doped semiconductor is thin enough that it can be completely depleted before avalanche breakdown occurs, the structure can exhibit many novel transport behaviors. Two outstanding features of the structure are that (1) a wide range of high-level injection of minority carriers can be achieved by varying the barrier heights of the two contacts and (2) the critical voltage at which the minority carrier injection increases rapidly can be varied by varying the semiconductor doping and thickness.

Experimental silicon MSM structures of PtSi-Si-PtSi have been made from n-type silicon with doping of 4×10¹⁴ cm⁻³ and thickness of 12 μm. The critical voltage at room temperature is about 30 V. The current increases over five orders of magnitude with only 10 per cent increase of the voltage. The above results and other measurements over wide temperature range do substantiate the theoretical predictions.     

Fast AlGaN metal-semiconductor-metal photodetectors grown onSi(111)

Metal-semiconductor-metal photodetectors have been fabricated on AlGaN grown on Si(111) by molecular beam epitaxy for solar-blind applications. A cutoff wavelength of 290 nm and an ultraviolet/visible contrast of more than three orders of magnitude are achieved. Time response measurements show fast exponential decays. With a minimum decay time of 150 ns. The photodetectors present responsivities that increase with bias, reaching 15 mA/W at 4 V bias     

AlxZn1-xO合金MSM光电探测器的研究

在Si衬底上磁控溅射制备AlxZn1-xO(AZO)合金薄膜,在其上真空蒸发Ni/Au叉指电极获得金属-半导体-金属(MSM)结构光电探测器.采用UV-Vis-Nir分光光度计测量AZO系列薄膜的光吸收特性,观察到AZO 合金薄膜的光学吸收带边随Al含量增加明显蓝移.测试AZO探测器的电流电压特性、时间特性和响应光谱发...     

Cryogenic processed metal-semiconductor-metal (MSM) photodetectorson MBE grown ZnSe

Molecular beam epitaxy grown 0.5-μm and 2.0-μm thick undoped ZnSe on semi-insulating (100) GaAs substrates were prepared for metal-semiconductor-metal (MSM) photodetector devices. The MSM photodetectors consisted of interdigitated metal fingers with 2, 3, and 4 μm width/spacing on a wafer. A multilayer resist process was employed using polyimide and SiO₂ thin films before the pattern generation to aid in a special low temperature (LT) lift-off process. Dark current-voltage (I-V), DC photo I-V, high frequency I-V, spectral response, and frequency response techniques were employed for testing the device performance. The cryogenic processed metallization provided an improved interface between metal and semiconductor interface. The breakdown voltage in these devices is dependent on the electrode width/spacing and not on film thickness. Dark current remained at around 1 pA for a bias of ±10 V. The devices exhibited a high spectral responsivity of 0.6 (A/W) at a wavelength of 460 nm at 5 V applied bias. A maximum spectral responsivity of 1 (A/W) at an applied bias of 5 V was obtained in these devices indicating an internal gain mechanism. This internal gain mechanism is attributed to hole accumulation in ZnSe epilayers     

Low dark current GaAs metal-semiconductor-metal (MSM) photodiodes using WSixcontacts

We present the fabrication and characterization of metal-semiconductor-metal (MSM) photodiodes using the same undoped GaAs layer that is used as a buffer layer in the epitaxial structure for GaAs field effect transistors (FET's). To study the dark current mechanism, various metal electrodes used for Schottky contacts are examined. A drastic V-shape relationship between the dark current of MSM photodiode and the Schottky barrier height is found. An extremely low dark current (a few nanoamperes) in the MSM photodiode is obtained by using tungsten silicide as electrode metal. It is concluded that the dark current is a function of a rivalry relation between the electron injection at the cathode and the hole injection at the anode. The internal gain of the MSM photodiode with tungsten silicide contacts is found, and possible mechanisms are discussed. A flat frequency response up to 1.3 GHz is obtained. The results shows the feasibility of MSM photodiodes for use as photodetectors with low minimum detectable power, and their applicability to monolithic integration with FET circuits.     

Pb_(1-x)Sn_xTe(LTT)中的扩散—Sb扩散的表面形貌

本文报告了在扩散中的气相生长现象、扩散气氛对基片表面形貌的影响。     

Low-noise solar-blind AlxGa1-xN-based metal-semiconductor-metal ultraviolet photodetectors

We report the growth, fabrication, and characterization of high performance Schottky metal-semiconductor-metal solar-blind photodetectors fabricated on epitaxial Al_0.4Ga_0.6N layers grown by metalorganic chemical vapor deposition. The devices exhibited low dark current (<2 pA at 30 V) and a gain-enhanced ultraviolet (UV) photocurrent for bias voltages >40 V. The gain was corroborated by external quantum efficiency measurements reflecting a quantum efficiency as high as 49% (at=272 nm) at 90 V bias, with a corresponding responsivity R=107 mA/W. A visible-to-UV rejection factor of more than three orders of magnitude was demonstrated. Time-domain and frequency-domain speed measurements show a 3-dB bandwidth of ∼100 MHz. Low-frequency noise measurements have determined a detectivity (D^*) as high as 3.3 10¹⁰ cm·Hz^1/2/W for a 500 Hz bandwidth at 37 V bias.     

Pb1—xGexTe薄膜的光学性质

对PVD沉积Pb1-xGexTe薄膜研究发现Pb1-xGexTe是一种高性能的红外材料,在3－25μm光谱范围具有较好的透光性能,室温下的折射率为4．8－5．6薄膜的光学性质,包括透射率、色散关系以及折射率的温度系数dn/dT,与材料中组分x、环境温度和薄膜的沉积工艺条件有密切关系,适当地改变组分和工艺条件,可以使薄膜的折射率温度系数dn/dT从负变到零并转为正,这对于制备高温度稳定性的红外光学薄膜器件具有重要的意义。     

水平无籽晶气相生长的Pb_(1-x)Sn_xTe二极管激光器

本文报告了采用HUVG方法制造的铅盐可调谐二极管激光器。在12K温度下,激光器的阈值电流为1.6安培,发射波长为10.2微米。     

Ultraviolet-visible metal-semiconductor-metal photodetectors fabricated from InxGa1−xN (0≤x≤0.13)

Metal-semiconductor-metal (MSM) photodetectors have been fabricated on In_xGa_1−xN epitaxial films grown by metalorganic chemical vapor deposition within the composition range 0≤x≤0.13. The dark current and spectral response were measured for devices with a varying In mole fraction x. The devices, which had nominal finger widths and finger spacing of 5 μm, were biased with modest voltages in the range 2≤V_bias≤5 V. In general, turn-on wave-length and dark current increased with increasing x. Turn-on wavelengths ranged from λ=370 nm to 430 nm and dark current densities ranged from I_dark=2×10⁻² A/cm² (V_bias=5 V, x≈0.05) to 9×10⁴ A/cm² (V_bias=2 V, x≈0.13) depending on the In content, x, of the device active area.     

Performance of a near-infrared GaAs metal-semiconductor-metal (MSM)photodetector with islands

A GaAs metal-semiconductor-metal (MSM) photodetector with ultrasmall gold islands deposited on its photosensitive surface is described. The interdigitated detector is fabricated on a semi-insulating substrate in a MESFET-compatible technology. Responsivity as high as 1.8 A/W is obtained at 0.86 μm and a bias voltage of 8 V. This represents over a sixfold increase with respect to responsivity of a conventional MSM photodetector. The mechanism for dark current is suggested and breakdown characteristics are presented     

Low-noise back-illuminated AlxGa1-xN-basedp-i-n solar-blind ultraviolet photodetectors

We report the growth, fabrication and characterization of Al_0.4Ga_0.6N-Al_0.6Ga_0.4N back-illuminated, solar-blind p-i-n photodiodes. The peak responsivity of the photodiodes is 27 and 79 mA/W at λ≈280 nm for bias voltages of 0 V and -60 V, respectively, with a UV-to-visible rejection ratio of more than three decades (at 400 nm). These devices exhibit very low dark current densities (~5 nA/cm² at -10 V). At low frequencies, the noise exhibits a 1/f-type behavior. The noise power density is S₀≈5×10^-25 A²/Hz at -12.7 V and the detectivity (D*) at 0 V is estimated to be in the range of 4×10¹¹-5×10¹³ cm·Hz^1/2 /W. Time-domain pulse response measurements in a front-illumination configuration indicate that the devices are RC-time limited and show a strong spatial dependence with respect to the position of the incident excitation, which is mainly due to the high resistivity of the p-type Al_0.4Ga_0.6 N layer