CdSe核辐射探测器中的MIS接触电极

对MIS(金属-绝缘体-半导体)接触电极的特性进行了系统的分析和实验观察.结果表明,负极的电子可以通过表面能级和热激发注入到CdSe晶片中,且晶片表面的电子能级密度越高,电子注入就越快,探测器的漏电流也越大.对探测器进行适当的热处理,可以降低表面能级密度,从而抑制电子注入,降低探测器的漏电流,改善探测器的能量分辨率.     

微重力条件下生长GaAs单晶的电学和光学性质研究

用多种实验手段分别对地面和太空生长的掺Te砷化镓单晶的电学、光学均匀性和深能级行为进行了实验研究.初步结果表明:在太空进行再生长的GaAs单晶电子浓度比原地面生长的籽晶小一个数量级,电子浓度由地面晶体到太空晶体的过渡是陡变的;DLTS测量发现太空单晶中存在两个电子陷阱,分别位于导带下0.27eV和0.60eV处,深能级密度为浅施主N_D的10~(-3)-10~(-4);少子注入未观察到空穴陷阱;用太空GaAs单晶为衬底制备的25个单异质结(SH)二极管,具有一致的I-V和发光特性,这反映了太空晶体的均匀性优于地面晶体.此外,还对太空生长GaAs单晶电子浓度降低的可能原因、深能级行为以及太空生长高质量晶体的前景作讨论.     

Hg_(1-x)Cd_xTe探测器表面积累层的磁输运特性

利用WKB近似对Hg1-xCdTe探测器表面积累层二维电子气的色散关系进行了计算，获得了不同表面电子浓度下，各子带的电子浓度、能级位置和有效质量．考虑了能带的非抛物性，由SdH振荡获得的结果与理论符合的很好．     

雪崩热电子注入对快速热氮化的SiO_xN_y膜陷阱的影响

本文研究了雪崩热电子注入对快速热氮化的SiO_zN_y膜体内电子陷阱和界面陷阱的影响.结果表明:快速热氮化的SiO_xN_y膜存在着不同类型的陷阱,其陷阱密度悬殊很大.雪崩热电子注入过程中在Si/SiO_xN_y界面上产生两类性质不同的快界面态陷阱.同时还给出这两种陷阱在禁带中的能级位置,界面态密度随雪崩注入的变化关系.文中并对实验结果进行讨论与分析.     

利用二次阳极氧化方法降低N型碲镉汞材料表面复合速度

利用微波反射光电导衰退法比较了采用一次阳极氧化和二次阳极氧化的N型碲镉汞材料的非平衡载流子寿命及其随温度的变化,通过与理论值进行比较拟合得到了碲镉汞材料表面复合速度随温度的变化曲线.结果发现,二次阳极氧化方法能够更好地降低材料表面悬挂键的密度,同时减少抛光引入的表面缺陷能级的数量,从而降低材料的表面复合速度,改善材料的非平衡载流子寿命,利于制造出高性能的HgCdTe红外探测器.     

n-GaN肖特基势垒紫外光探测器的电子辐照效应

研究了n型Au/GaN肖特基势垒紫外光探测器的电子辐照失效机理.从实验中观测到,随着电子辐照注量的不断增加,Au/GaN间辐照诱生的界面态引起器件的击穿电压明显减小,反向漏电流逐渐增大.辐照诱生的深能级缺陷导致紫外光探测器对较长波长光的吸收,使得UV探测器中可见光成分的背景噪声增加.同时,对辐照后的GaN肖特基紫外光探测器进行了100℃以下的退火处理,退火后,器件的电流-电压特性有所改善.     

采用P^＋共同注入改进SI—GaAs Si^＋注入层的电特性

在SI—GaAs Si~+注入层中共同注入P~+可以改进注入层的电特性。P~+的共同注入提高了注入层的激活率和平均霍耳迁移率。对于Si~+注入的剂量和能量分别为4×10~(12)cm~(-2)/30keV+5×10~(12)cm~(-2)/130keV的样品,得到了激活率为75～85％,平均霍耳迁移率为4600～4700cm~2/Vs的结果。另一方面,P~+注入改进了有源层与衬底的界面特性。肖特基势垒技术测量表明,P~+共同注入的样品表现出更好的迁移率分布。深能级瞬态谱(DLTS)测量表明,P~+共同注入降低了激活层中的深能级密度。     

半导体纳米颗粒载流子的超快弛豫过程

分析了纳米颗粒的能级结构,建立了载流子弛豫的简化模型,运用数值模拟方法讨论了激发密度、表面态密度及俘获态电子的弛豫率对弛豫过程的影响。讨论结果表明,激发密度的增大及表面态的减少都会导致表面态上电子的饱和,使导带上出现电子的积累,导带电子寿命增大;深俘获态电子的弛豫是影响材料响应速度的主要因素。最后应用此模型对近红外泵浦探测实验的结果进行分析,表明模型可望在实验结果分析上得到应用。     

ICP刻蚀损伤对n-GaN-Ni/Au肖特基接触特性的影响

通过电流-电压法(I-V),电容-电压法(C-V)对n-GaN材料的ICP(感应耦合等离子体)刻蚀样品和未刻蚀样品上的肖特基势垒二极管的电学特性进行了分析.利用原子力显微镜(AFM)和扫描电镜(SEM)对刻蚀样品的表面形貌,以及退火前后肖特基接触金属的表面形貌变化进行了研究.试验表明,ICP刻蚀会在GaN表面引入损伤,形成电子陷阱能级从而引起肖特基二极管的势垒高度降低,理想因子增大,反向泄漏电流增大.刻蚀样品在400 ℃热退火可以恢复二极管的电特性,退火温度到600 ℃时二极管特性要好于未刻蚀的样品.     

带隙渐变纳米线的光电导淬灭效应

采用气相沉积温度梯度分布合成纳米线法,在750～950℃耐高温石英管中,在催化剂金的催化作用下,生长出310μm带隙渐变的硫硒化镉半导体纳米线,并利用倏逝波耦合的方法导波激发,分别对不同掺杂比例的部分纳米线进行研究。实验发现,在注入功率低于10-8 W时,随着光强增大不同带隙宽度的纳米线的淬灭度都在增大;然而在注入功率继续增大时,S元素比例占到90%的纳米线的淬灭度峰值最早到来,以Se元素为主的纳米线的淬灭度峰值在10-6 W注入光下仍未出现,原因是增加S元素会使更多的复合中心转变为陷阱能级中心,更多的电子可以跃迁至导带。封装上电极的带隙渐变纳米线可应用于制作高分辨率的红外光探测器,也为有效检测半导体材料的缺陷能级提供了便利。     

甚长波碲镉汞光伏探测器伏安特性分析

分析了注入同质结N on P和液相外延异质结P on N碲镉汞甚长波红外探测器在不同工作温度下的I V特性,并对R V特性进行了仿真计算,对比了扩散电流、产生-复合电流、表面漏电流、带间隧穿电流和缺陷辅助隧穿电流等暗电流对两种器件R V特性的不同影响。     

Hg1-xCdxTe光伏探测器的表面漏电流机制及其钝化

表面漏电流能对Hg1-xCdxTe光伏探测器性能产生很大的影响,因此选择合适的钝化工艺尤其重要。本文主要论述了Hg1-xCdxTe光伏探测器表面漏电流机制及其钝化技术的发展状况。     

气态源分子束外延生长扩展波长InGaAs探测器性能分析

从理论与实验两方面对截止波长为1.7μm(x=0.53),1.9μm(x=0.6)和2.2μm(x=0.7)p in InxGa1-xAs探测器性能进行了研究.对探测器暗电流的研究结果表明,扩展波长In0.6Ga0.4As,In0.7Ga0.3As探测器在反向偏置低压区,欧姆电流占据主导地位;在反向偏置高压区,缺陷隧穿电流占主导地位;且扩展波长In0.6Ga0.4As,In0.7Ga0.3As探测器的暗电流比In0.53Ga0.47As探测器增加较大.对探测器R0A随温度及i层载流子浓度变化关系的研究结果表明,在热电制冷温度下探测器性能可得到较大提高,i层的轻掺杂可使探测器的R0A得到改善.     

Analysis of dark current in IR detectors on thinned p-type HgCdTe

A model for the diffusion dark current in MIS IR detectors on thinned bulk p-type HgCdTe is discussed. The model includes trap-assisted tunneling mechanisms in the back-side depletion region as well as the effects of fast surface states. Expressions for the net recombination rate are developed for situations in which trap-assisted tunneling transitions are allowed. Calculations for 12-μm optical cutoff detectors operating at liquid-nitrogen temperature show that the properties of the back side, including surface fixed charge density, depletion region trap density, fast surface-state density, and majority carrier concentration, have a strong influence on the dark current levels of detectors on thin material. It is predicted that typical as-fabricated surface parameters will not result in large dark current densities. Calculations for detectors with surface parameters common to stressed (degraded) back surfaces, however, show dark current densities which would significantly affect detector performance     

SiO_2钝化层对GaN基PIN结构核探测器漏电流的影响

成功地制备了有SiO2钝化层和无SiO2钝化层的GaN基PIN结构核辐射探测器,并对二者的I-V特性进行了测试。实验结果表明,SiO2钝化层的存在显著地降低了GaN基PIN结构核辐射探测器的反向漏电流,在-40V的反向偏压情况下,漏电流约有2个数量级的降低。实验过程中观测到随着反向偏压的增大,SiO2钝化层对器件反向漏电流的抑制效应更明显。建立了一种表面沟道模型解释了SiO2钝化层对漏电流的影响。     

Effect of device processing on 1/f noise in uncooled, auger-suppressed CdHgTe diodes

Auger suppression reduces the leakage current in uncooled CdHgTe diodes to the point where the shot noise limited D* is significantly higher than for other uncooled detectors. However, Auger-suppressed diodes exhibit high levels of 1/f noise and so applications have initially been in devices operating at high frequency such as CO₂ laser heterodyne detectors. In order to use Auger suppression in imaging devices, we need to reduce the 1/f noise and this paper describes a study of the effects of device processing on noise. We find that although some of the noise is associated with perimeter leakage currents, variations in the surface passivation treatment have little effect on the total noise. However, a post-passivation anneal can reduce the noise in some cases. We also find that CdTe passivated devices are more stable when baked than those passivated with ZnS.     

Surface passivation of cadmium zinc telluride radiation detectors by potassium hydroxide solution

The spectral resolution of cadmium zinc telluride (CZT) room temperature nuclear radiation detectors is often limited by the presence of conducting surface species that increase the surface leakage current. Surface passivation plays an important role in reducing this surface leakage current and thereby decreasing the noise of the detectors and improving the spectral energy resolution. Chemical etching with a Br-MeOH solution leaves CZT surfaces rich in Te and is considered as one of the primary causes of the increased surface leakage current. Previous studies have shown that hydrogen peroxide (H₂O₂) forms oxides of tellurium on the CZT surface and thus acts as a good passivating agent. In this study we will present results on the use of potassium hydroxide (KOH) as an alternative passivating agent. The KOH aqueous solution leaves a more stoichiometric (evaluated from the trends in the surface Cd:Te ratio) and smoother CZT surface. The passivation effects of KOH solution on the surface of the CZT have been characterized by current-voltage measurements for different KOH concentrations and etching times for both parallel strip electrodes as well as a metal-semiconductor-metal configuration. The surface chemical composition and its morphology were studied by scanning x-ray photoelectron spectroscopy and atomic force microscopy. The comparison and demonstration of improvements in the spectral resolution of the CZT detectors (based on ²⁴¹Am spectra) with and without the KOH treatment are presented.     

Point Defects in Pb-, Bi-, and In-Doped CdZnTe Detectors: Deep-Level Transient Spectroscopy (DLTS) Measurements

We studied, by current deep-level transient spectroscopy (I-DLTS), point defects induced in CdZnTe detectors by three dopants: Pb, Bi, and In. Pb-doped CdZnTe detectors have a new acceptor trap at around 0.48?eV. The absence of a V_Cd trap suggests that all Cd vacancies are compensated by Pb interstitials after they form a deep-acceptor complex [[Pb_Cd]⁺-V _Cd ^2? ]^?. Bi-doped CdZnTe detectors had two distinct traps: a shallow trap at around 36?meV and a deep donor trap at around 0.82?eV. In detectors doped with In, we noted three well-known traps: two acceptor levels at around 0.18?eV (A-centers) and 0.31?eV (V_Cd), and a deep trap at around 1.1?eV.     

碲镉汞光伏探测器的变面积表面钝化研究

利用同一片碲镉汞材料制备了由单层ZnS和双层CdTe/ZnS作钝化膜的变面积光伏探测器,对两种钝化膜结构的变面积器件进行了对比研究.通过分析两种器件的电流-电压(I-V)特性曲线以及零偏电阻-面积乘积(RoA)与周长-面积比(p/A)的关系曲线,发现ZnS钝化的器件具有较大的表面漏电流;通过分析两种器件的电流噪声与暗电流的关系,发现ZnS钝化的器件的噪声特性较接近散粒噪声,CdTe/ZnS双层钝化的器件则表现出较好的基本1/f噪声特性,使得器件噪声要小于单层ZnS钝化的器件.     

超薄氧化层中的中性陷阱对隧穿电流的影响和应变诱导漏电流

用数值分析的方法讨论了中性陷阱对超薄场效应晶体管(MOSFET )隧穿电流的影响.中性陷阱引起势垒的变化在二氧化硅的导带中形成一个方形的势阱.对于不同的势垒变化,计算了电子隧穿氧化层厚度为4nm的超薄金属氧化物半导体结构的电流.结果表明,中性陷阱对隧穿电流的影响不能被忽略,中性陷阱的存在使隧穿电流增加,并且通过这个简单的模型能够理解应变诱导漏电流的产生机制.