近红外响应的III-V族半导体光电阴极材料及工艺

随着GaAs负电子亲和势(NEA)半导体光电阴极在我国的成熟和应用,半导体光电阴极的进一步研究将往更长波的近红外发展。针对透射式半导体光电阴极器件,系统总结了近红外波段响应良好的GaAs、InGaAs、InGaAsP Ⅲ-V族外延材料特性及相应商业化产品的应用领域和性能。通过文献调研本文进一步归纳了不同波段NEA光电阴极和转移电子光阴极适用的材料结构,并结合传统GaAs NEA光电阴极工艺讨论了InGaAs、InGaAsP材料及阴极工艺的难点。     

近红外响应的Ⅲ-V族半导体光电阴极材料及工艺北大核心

随着GaAs负电子亲和势(NEA)半导体光电阴极在我国的成熟和应用,半导体光电阴极的进一步研究将往更长波的近红外发展。针对透射式半导体光电阴极器件,系统总结了近红外波段响应良好的GaAs、InGaAs、InGaAsP Ⅲ-V族外延材料特性及相应商业化产品的应用领域和性能。通过文献调研本文进一步归纳了不同波段NEA光电阴极和转移电子光阴极适用的材料结构,并结合传统GaAs NEA光电阴极工艺讨论了InGaAs、InGaAsP材料及阴极工艺的难点。     

负电子亲和势冷阴极

负电子亲和势冷阴极是在负电子亲和势光阴极的基础上发展起来的,目前已报道的负电子亲和势冷阴极有GaAs、Si、GaAsP、GaP、GaAlP等。这些晶体材料也都是光阴极,有不同程度的光电发射。对外延生长、外延层质量、超高真空技术与表面原子清洁度的要求以及Cs、O_2激活工艺等方面,负电子亲和势冷阴极与负电子亲和势光     

第三代象增强器

引言三代象增强器是一种采用GaAs光电阴极的双近贴象管。二代管和三代管的主要差别在于光电阴极。1965年负电子亲和势光电阴极的发现是新型光电发射作研究的起点。1975年Antypas和Edgecumbe实现了GaAs/GaAlAs双异质结结构,为制作高质量GaAs透射式光电阴极提供了可能性。从那时起,人们就着手研究三代象增强器。在GaAs光电阴     

光谱响应范围为0.7-1.65μm的一种近红外光阴极

(一)前言 众所周知,夜视仪器最基本的要求是看得远、看得清。夜视仪器中主要的部件除光学透镜外就是微光管。而光阴极则是微光管的“眼睛”。目前,二、三代微光管中的光阴极分别为Sb-K-Na-Cs与GaAs,它们的长波阈约为0.9μm。夜天空辐射强度是满月与星空交替变化的。满月以可见光辐射为主,而星空则以近红外辐射为主。在星空辐射下,波长大于1μm的辐射强度比可见光的辐射强度约大1—2个数量级。因此,Sb-K-Na-Cs与GaAs两种光阴极用于微光管内接收夜天空辐射,对满月是可以的,但是对波长长于0.9μm     

负电子亲和势氮化镓光电阴极

负电子亲和势GaN光电阴极在紫外探测技术领域具有诱人的应用前景.本文在介绍和分析负电子亲和势GaN光电阴极的特点、工作原理及其能带结构的基础上,设计了GaN外延材料的结构和阴极制作工艺.指出负电子亲和势GaN光电阴极制备的关键在于材料的生长、与输入光窗的融焊、衬底的减薄及彻底的去气处理和超高真空状态下的铯、氧激活.     

NEA GaN基双色集成光电阴极的理论模型与结构优化

本文设计了一种负电子亲和势Ga N基光电阴极量子级联结构的紫外-红外双色集成探测器模型,通过Nextnano与Silvaco TCAD软件研究光电阴极的量子级联层周期数、势阱层厚度、传输层Al组分、光照角度以及光进入阴极方向等。优化后的仿真结果表明：量子级联层10～20周期,p-GaN势阱层厚度为2nm,传输层Al组分为0.4,红外波段光照角度范围为120°～130°时器件探测性能好。紫外波段响应峰值波长300nm,响应度约为52.97mA/w;红外波段响应峰值波长在1.4μm～1.6μm之间,响应度约为3.92～3.96mA/w。同时仿真显示该光电阴极反射式性能优于透射式。     

高积分光电灵敏度多层Be浓度掺杂的GaAs负电子亲和势光电阴极

研究了变掺杂浓度结构对GaAs负电子亲和势光电阴极积分光电灵敏度的影响.通过MBE生长了两组GaAs同质外延样品.其中一组采用了均匀掺杂的单层结构,Be掺杂浓度为1×1019cm-3;另一组采用了变掺杂的多层结构,从衬底开始Be的掺杂浓度依次为1×1019,7×1018,4×1018和1×1018cm-3.负电子亲和势光电阴极通过在高真空系统中交替通入Cs和O激活得到.在线光谱响应测试曲线表明,多层Be掺杂结构光阴极的积分光电灵敏度比单层Be掺杂结构光阴极的积分光电灵敏度至少提高了50%.两种结构的GaAs样品表现出不同的表面应力情况.     

InGaAs光电阴极像增强器研究

ＩｎＧａＡｓ 光电阴极像增强器的光谱为１－０ ～１－３μｍ 和１－０ ～１－１μｍ 。对用于像增强器中的ＩｎＧａＡｓ 光电阴极进行了研究。研究的方法有：光致发光法、微型瑞曼法、扫描俄歇俄法。将ＩｎＧａＡｓ 像增强器的光谱和标准的第二代和第三代像增强器进行比较。文中还报导了负电子亲和势ＩｎＧａＡｓ 光电阴极摄像管的性能参数：光谱灵敏度、白光光响应、等效背景照度、信噪比、调制传递函数以及像增强器的性能。对ＩｎＧａＡｓ 负电子亲和势光电阴极和标准第二代像增强器阴级直接进行比较。最后评价了近红外ＩｎＧａＡｓ 光电阴极像增强器的先进性。     

负电子亲和势光电阴极50年史话

本文是负电子亲和势光电阴极发现50周年的纪念文章,简要回顾了过去的成绩,现在的困难及今后的展望。经过近30年的努力,我国 MOCVD 生长的反射式 GaAs 光电阴极的积分灵敏度已达到3516μA/lm,目前存在的困难是光电阴极寿命问题,寿命问题解决了,高性能微光像增强器以及EBAPS 数字器件可以缩短与西方的差距。如果高灵敏度长寿命的 GaAs：O-Cs 光电阴极真正取代了目前大科学装置中的铜阴极,基于我国大科学装置的基础研究才会迎来真正的科学春天。     

Electron transport in an In<Subscript>0.52</Subscript>Al<Subscript>0.48</Subscript>As/In<Subscript>0.53</Subscript>Ga<Subscript>0.47</Subscript>As/In<Subscript>0.52</Subscript>Al<Subscript>0.48</Subscript>As quantum well with a δ-Si doped barrier in high electric fields

The electron conduction in a two-dimensional channel of an In_0.52Al_0.48As/In_0.53Ga_0.47As/In_0.52Al_0.48As quantum well (QW) with a δ-Si doped barrier has been investigated. It is shown that the introduction of thin InAs barriers into the QW reduces the electron scattering rate from the polar optical and interface phonons localized in the QW and increases the electron mobility. It is found experimentally that the saturation of the conduction current in the In_0.53Ga_0.47As channel in strong electric fields is determined by not only the sublinear field dependence of the electron drift velocity, but also by the decrease in the electron concentration n _s with an increase in the voltage across the channel. The dependence of n _s on the applied voltage is due to the ionized-donor layer located within the δ-Si doped In_0.52Al_0.48As barrier and oriented parallel to the In_0.53Ga_0.47As QW.     

Ultrafast Dynamics of Photoexcited Charge Carriers in In<Subscript>0.53</Subscript>Ga<Subscript>0.47</Subscript>As/In<Subscript>0.52</Subscript>Al<Subscript>0.48</Subscript>As Superlattices under Femtosecond Laser Excitation

The results of experimental studies of the time dynamics of photoexcited charge carriers in In_0.53Ga_0.47As/In_0.52Al_0.48As superlattices grown by molecular-beam epitaxy on a GaAs substrate with a metamorphic buffer are reported. On the basis of the results of the numerical simulation of band diagrams, the optimal thickness of the In_0.52Al_0.48As barrier layer (4 nm) is chosen. At this thickness, the electron wave functions in In_0.53Ga_0.47As substantially overlap the In_0.52Al_0.48As barriers. This makes it possible to attain a short lifetime of photoexcited charge carriers (τ ~ 3.4 ps) at the wavelength λ = 800 nm and the pumping power 50 mW without doping of the In_0.53Ga_0.47As layer with beryllium. It is shown that an increase in the wavelength to λ = 930 nm (at the same pumping power) yields a decrease in the lifetime of photoexcited charge carriers to τ ~ 2 ps. This effect is attributed to an increase in the capture cross section of trapping states for electrons with lower energies and to a decrease in the occupancy of traps at lower excitation densities.     

Persistent photoconductivity and electron mobility in In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As/InP quantum-well structures

The influence of the width of the quantum well L and doping on the band structure, scattering, and electron mobility in nanoheterostructures with an isomorphic In_0.52Al_0.48As/In_0.53Ga_0.47As/In_0.52Al_0.48As quantum well grown on an InP substrate are investigated. The quantum and transport mobilities of electrons in the dimensionally quantized subbands are determined using Shubnikov-de Haas effect measurements. These mobilities are also calculated for the case of ionized-impurity scattering taking into account intersub-band electron transitions. It is shown that ionized-impurity scattering is the dominant mechanism of electron scattering. At temperatures T < 170 K, persistent photoconductivity is observed, which is explained by the spatial separation of photoexcited charge carriers.     

Super-flat interfaces in In0.53Ga0.47As/In0.52Al0.48As quantum wells grown on (411)A InP substrates by molecular beam epitaxy

Effectively atomically flat interfaces over a macroscopic area (“(411)A super-flat interfaces”) were successfully achieved in In_0.53Ga_0.47As/In_0.52Al_0.48As quantum wells (QWs) grown on (411)A InP substrates by molecular beam epitaxy (MBE) at a substrate temperature of 570°C and V/III=6. Surface morphology of the In_0.53Ga_0.47As/In_0.52Al_0.48As QWs was smooth and featureless, while a rough surface of those simultaneously grown on a (100) InP substrate was observed. Photoluminescence (PL) linewidths at 4.2 K from the (411)A QWs with well width of 0.6–12 nm were 20–30 % narrower than those grown on a (100) InP substrate and also they are almost as narrow as each of split PL peaks for those of growth-interrupted QWs on a (100) InP substrate. In the case of the (411)A QWs, only one PL peak with very narrow linewidth was observed from each QW over a large distance (7 mm) on a wafer.     

MOCVD of Ga0.52In0.48P Using Tertiarybutylphosphine

Tertiarybutylphosphine was explored as a safer alternative to phosphine for the atmospheric pressure chemical vapor deposition of Ga_0.52In_0.48P on GaAs. For V/III ratios greater than or equal to 50 and growth temperatures between 630 and 700° C, the minority carrier diffusion length of Ga_0.52In_0.48P grown from t-butylphosphine, approached that of Ga_0.52In_0.48P grown from phosphine under similar conditions. Compared to deposition with phosphine, with t-butylphosphine the surface morphology was rougher, the carbon and sulfur contamination was greater, and the loss of indium by parasitic reaction was greater. The band gap of the Ga_0.52In_0.48P at fixed composition varied differently with V/III ratio.     

Controllable growth of semiconductor nanometer structures

Self-assembled quantum dots and wires were obtained in the In_xGa_1-xAs/GaAs and InAs/In_0.52Al_0.48As/InP systems, respectively, using molecular beam epitaxy (MBE). Uniformity in the distribution, density, and spatial ordering of the nanostructures can be controlled to some extent by adjusting and optimizing the MBE growth parameters. In addition, some interesting observation on the InAs wire alignment on InP(001) is discussed.     

InAs Wires on InP (001)

在分子束外延生长的InAs/In0.52Al0.48As/InP异质结体系中,形成InAs量子线.这些InAs量子线在生长和结构方面有一些独到的特性,并介绍了本实验室在研究InAs量子线的生长和结构方面所做的工作.     

Thermal stability of Al0.48In0.52As/Ga0.47In0.53As/InP heterostructure and its improvement by phosphidization

A drastic decrease in the sheet carrier concentration of modulation-doped Al_0.48In_0.52As/Ga_0.47In_0.53As/InP heterostructures has been observed after O₂ plasma treatment followed by thermal treatment up to 350°C. The decrease in sheet carrier concentration, which is speculated to be caused by both plasma damage and impurities penetrating from the surface of the epilayer, can be suppressed substantially by using PH₃ plasma treatment prior to the O₂ plasma and thermal treatments.     

The dependence of the electrical and optical properties of molecular beam epitaxial Ino.52Alo.48As on growth parameters: Interplay of surface kinetics and thermodynamics

The optical and transport properties of In_0.52Al_o.48As grown by molecular beam epitaxy have been studied as a function of growth temperature in the range of 300-520° C. It is evident that under our growth conditions, thermodynamic considerations become important, and combined with surface kinetics, clustering effects become most severe for growth temperatures around 400° C. The clustering effects are manifested by changes in low-temperature photoluminescence, Hall transport and in the properties of Schottky diodes made on the films and the relevant parameters show a peaking for growth at 400° C. In particular, the Hall mobility exhibits a turning point forT > 300 K, beyond which the mobility increases with increasing temperature. In addition, the Hall electron concentration exhibits an anomalous reduction in value in the same high-temperature range. Measurements were also made on In_0.52Al_0.48As grown at 620-650° C by metalorganic chemical vapor deposition. While these films exhibit the same turning point in Hall mobility, the reduction in carrier concentration is significantly absent. Analysis of these data therefore indicates that the turning point in the mobility, which is present for both growth techniques, is caused by small clusters (~35Å) of phases slightly different from the mean composition. The reduction in electron concentration, seen only in the molecular beam epitaxial samples, suggest a more severe phase separation. A simple analysis for the sample grown at 400° C indicates that the compositions In_0.60Al_0.40As and In_0.44Al_0.56As might be present, in addition to the mean lattice-matched composition.     

Highly confined two-dimensional electron gas in an In0.52AI0.48As/In0.52Ga0.47As modulation-doped structure with a strained InAs quantum well

This paper examines a detailed analysis by Shubnikov-de Haas measurements of the effective mass of two-dimensinal electron gas (2DEG) in an In_0.52Al_0.48As/ In_0.53Ga_0.47As modulation-doped (MD) structure with an InAs quantum well inserted into the InGaAs channel (InAs-inserted channel). The measured effec-tive mass of 2DEG in the InAs-inserted-channel MD structure is in good agreement with the calculated one of the strained InAs layer on In_0.53Ga_0.47As. This indicates that almost all of the 2DEG forms in the strained InAs quantum well. These results show that the InAs-inserted-channel MD structure improves the electron confinement, since the 2DEG is confined in the InAs quantum well with the thickness of 4 nm.