Hg1-xCdxTe metal-semiconductor-metal (MSM)photodetectors

Metal-semiconductor-metal (MSM) detectors with active layers of Hg _1-xCd_xTe (x=0.62-0.74) and electrode spacings of 2, 4, and 6 μm have been fabricated and characterized. Direct-current measurements have shown a low dark current and high responsivity from 0.15 to 1.5 A/W at 10-V bias. The lowest values of dark current (0.16 mA cm²) were obtained for detectors which incorporated an overlayer of CdTe. For detectors without the overlayer, increasing the Cd mole fraction resulted in a decrease in the dark current and a reduction in the 300-nm responsivity. Measurements of frequency response for these detectors show a maximum loss of 8 dB to 20 GHz. These results compare favorably with high-performance MSM detectors based on In_0.53Ga_0.47As with a lattice-matched barrier layer of In_0.52Al_0.48As     

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     

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。     

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.     

High efficiency long wavelength VCSEL on InP grown by MOCVD

High efficiency continuous-wave operation of 1.53 /spl mu/m vertical cavity surface emitting lasers (VCSELs) with buried tunnel junction grown by metal organic chemical vapour deposition (MOCVD) has been demonstrated. Devices show a high differential quantum efficiency of 46% and a singlemode power of 1 mW. Minimum threshold current and voltage are 0.45 mA and 1.3 V at room temperature, respectively for devices of 5 /spl mu/m diameter.     

Millimeter-wave ion-implanted gradedInxGa1-xAs MESFETs grown by MOCVD

The authors present the fabrication and characterization of ion-implanted graded In_xGa_1-xAs/GaAs MESFETs. The In_xGa_1-xAs layers are grown on GaAs substrates by MOCVD (metal-organic chemical vapor deposition) with InAs concentration graded from 15% at the substrate to 0% at the surface. 0.5-μm gate MESFETs are fabricated on these wafers using silicon ion implantation. In addition to improved Schottky contact, the graded In_xGa _1-xAs MESFET achieves maximum extrinsic transconductance of 460 mS/mm and a current-gain cutoff frequency f_t of 61 GHz, which is the highest ever reported for a 0.5-μm gate MESFET. In comparison, In_0.1Ga_0.9As MESFETs fabricated with the same processing technique show an f_t of 55 GHz     

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。     

竖直液相外延炉生长Pb_(1-x)Sn_xTe/PbTe_(1-y)Se_y晶格匹配异质结激光器

本文根据Vagard定律,得到了Pb_(1-x)Sn_xTe/PbTe_(1-y)Se_y异质结晶格匹配条件,设计了生长参数,首次采用竖直液相外延炉生长了Pb_(1-x)Sn_xTe/PbTe_(1-y)Se_y品格匹配异质结,并制成了二极管激光器。     

Molecular beam epitaxy grown long wavelength infrared HgCdTe on Si detector performance

The use of silicon as a substrate alternative to bulk CdZnTe for epitaxial growth of HgCdTe for infrared (IR) detector applications is attractive because of potential cost savings as a result of the large available sizes and the relatively low cost of silicon substrates. However, the potential benefits of silicon as a substrate have been difficult to realize because of the technical challenges of growing low defect density HgCdTe on silicon where the lattice mismatch is ∼19%. This is especially true for LWIR HgCdTe detectors where the performance can be limited by the high (∼5×10⁶ cm⁻²) dislocation density typically found in HgCdTe grown on silicon. We have fabricated a series of long wavelength infrared (LWIR) HgCdTe diodes and several LWIR focal plane arrays (FPAs) with HgCdTe grown on silicon substrates using MBE grown CdTe and CdSeTe buffer layers. The detector arrays were fabricated using Rockwell Scientific’s planar diode architecture. The diode and FPA and results at 78 K will be discussed in terms of the high dislocation density (∼5×10⁶ cm²) typically measured when HgCdTe is grown on silicon substrates.     

HgCdTe/Si materials for long wavelength infrared detectors

The heteroepitaxial growth of HgCdTe on large-area Si substrates is an enabling technology leading to the production of low-cost, large-format infrared focal plane arrays (FPAs). This approach will allow HgCdTe FPA technology to be scaled beyond the limitations of bulk CdZnTe substrates. We have already achieved excellent mid-wavelength infrared (MWIR) and short wavelength infrared (SWIR) detector and FPA results using HgCdTe grown on 4-in. Si substrates using molecular beam epitaxy (MBE), and this work was focused on extending these results into the long wavelength infrared (LWIR) spectral regime. A series of nine p-on-n LWIR HgCdTe double-layer heterojunction (DLHJ) detector structures were grown on 4-in. Si substrates. The HgCdTe composition uniformity was very good over the entire 4-in. wafer with a typical maximum nonuniformity of 2.2% at the very edge of the wafer; run-to-run composition reproducibility, realized with real-time feedback control using spectroscopic ellipsometry, was also very good. Both secondary ion mass spectrometry (SIMS) and Hall-effect measurements showed well-behaved doping and majority carrier properties, respectively. Preliminary detector results were promising for this initial work and good broad-band spectral response was demonstrated; 61% quantum efficiency was measured, which is very good compared to a maximum allowed value of 70% for a non-antireflection-coated Si surface. The R₀A products for HgCdTe/Si detectors in the 9.6-μm and 12-μm cutoff range were at least one order of magnitude below typical results for detectors fabricated on bulk CdZnTe substrates. This lower performance was attributed to an elevated dislocation density, which is in the mid-10⁶ cm⁻² range. The dislocation density in HgCdTe/Si needs to be reduced to <10⁶ cm⁻² to make high-performance LWIR detectors, and multiple approaches are being tried across the infrared community to achieve this result because the technological payoff is significant.     

Contact noise in n-type Hg1-xCdxTe photoconductors at 77 K

When gold wires are bonded to indium contacts on n-type Hg1-xCdxTe photoconductors with silver paste, the contacts are very noisy when carrying current. In all cases, the noisy contacts inject electrons into the sample when the contact acts as a cathode; in the poorest contacts, the noisy contact also injects holes when the polarity is reversed. The problem can be avoided by soldering the gold wires to the Hg1-xCdxTe samples with In solder or by bonding the gold wire to evaporated In contacts with the help of silver epoxy.     

Long wavelength infrared 128×128 AlxGa1-xAs/GaAs quantum well infrared camera and imaging system

The authors discuss the development of a long-wavelength (8-14-μm) 128×128 Al_xGa_1-xAs/GaAs multiquantum well infrared (MQW IR) imaging system. Highly uniform, high-yield GaAs focal plane arrays, incorporating an integral grating structure for efficient optical coupling, were hybridized to CMOS multiplexers. Excellent imagery, with low noise, a noise equivalent differential temperature (NEΔT) of less than 10 mK, and a high image contrast signal-to-noise ratio, has been achieved. It is shown that figures of merit concerning array uniformity, such as yield, NEΔT, and maximum deliverable charge to the CMOS multiplexer are much more relevant variables that affect image quality than D*     

Pb_(1-x)Sn_xTe和Pb_(1-y)Sn_ySe激光晶体

本文报道了具有合适的载流子浓度,低位错密度和适当p-n结深度的Pb_(1_x)Sn_xTe 和Pb_(1_υ)Sn_υSe激光晶体。这种晶体是用水平无籽晶气相生长技术和适当控制生长条件直接得到的,用这两种晶体已经制成OW运转的可调谐二极管激光器。     

Cd1-xZnxTe太阳电池的一维数值模拟研究

具有禁带宽度在1.45～2.25eV连续可调特性的Cd1-xZnxTe(CZT)薄膜,用于顶电池在叠层薄膜太阳电池中有巨大的应用潜力。文章使用AMPS-1D对CdS/CZT结构的薄膜太阳电池进行模拟,研究了CZT与金属接触的背电极势垒、CZT薄膜厚度及掺杂浓度对CdS/CZT电池器件性能的影响。结果表明,需要采用功函数高(大于5.8eV)的金属作为背电极以消除背电极势垒;CZT薄膜厚度低于10μm时,增加厚度有助于增大电池短路电流;当CZT具有适当厚度(～6μm)时,对CZT层进行重掺杂(掺杂浓度1019～1021 cm-3)有助于获得更高效率的CdS/CZT电池。     

The interface between Hg1−xCdxTe and its native oxide

The results of a study of the electrical properties of the interface between Hg_1?xCd_xTe with x = 0.21 and its native oxide at 77°K are presented. The native oxide is formed by anodic oxidation and results in an interface with reproducible properties. The surface charge, the surface mobility and the effective lifetime are obtained from galvanomagnetic measurements and are related to the semiconductor bulk parameters, the oxide thickness and the annealing conditions. The surface state charge and the metal-semiconductors work function difference are obtained from the shift of the flat band voltage of metal-oxide-semiconductor (MOS) capacitor characteristics. The interface between Hg_1?xCd_xTe and its native anodic oxide is characterized by a density of fast surface states of the order of 5 × 10¹¹cm^?2 (eV^?1) near the middle of the bandgap. The density of states increases towards the band edges to the order of 10¹³cm^?2 (eV^?1). The measured flat band voltage is approximately ?0.5 V for an oxide thickness of 500 Å and for an n-type semiconductor with an electron carrier concentration in the range 1–3 × 10¹⁵cm^?3 at 77°K. The fixed oxide surface state charge is positive for both p-type and n-type semiconductors and is of the order of 6 × 10¹¹ charges per cm^?2. The surface properties, the significance and the reproducibility of the results are evaluated.     

Low-resistance bandgap-engineeredW/Si1-xGex/Si contacts

Bandgap-engineered W/Si_1-xGe_x/Si junctions (p⁺ and n⁺) with ultra-low contact resistivity and low leakage have been fabricated and characterized. The junctions are formed via outdiffusion from a selectively deposited Si_0.7Ge _0.3 layer which is implanted and annealed using RTA. The Si _1-xGe_x layer can then be selectively thinned using NH₄OH/H₂O₂/H₂O at 75°C with little change in characteristics or left as-deposited. Leakage currents were better than 1.6×10^-9 A/cm² (areal), 7.45×10^-12 A/cm (peripheral) for p⁺/n and 3.5×10^-10 A/cm² (peripheral) for n⁺/p. W contacts were formed using selective LPCVD on Si_1-xGe_x. A specific contact resistivity of better than 3.2×10^-8 Ω cm² for p ⁺/n and 2.2×10^-8 Ω cm² for n⁺/p is demonstrated-an order of magnitude n⁺ better than current TiSi₂ technology. W/Si_1-xGe _x/Si junctions show great potential for ULSI applications