用正电子湮没方法鉴别InP半导体中的缺陷

本文测量了各种ＩｎＰ样品中的正电子寿命谱，用正电子湮没率连续分布测量（ＣＯＮ－ＴＩＮ分析）结合ＰＡＴＦＩＴ分析正电子寿命谱，肯定了在ｎ型和半绝缘型ＩｎＰ中有Ｉｎ空位ＶＩｎ和Ｐ空位ＶＰ，而在ｐ型ＩｎＰ中只观察到Ｉｎ空位ＶＩｎ．正电子寿命的温度关系表明所观察到的ｎ型和半绝缘型中的ＶＩｎ和ＶＰ以及ｐ型ＩｎＰ中的ＶＩｎ均为电中性．改进了常规的多普勒展宽谱仪．利用这一谱仪测量了ｎ型及半绝缘型ＩｎＰ的多普勒展宽谱，结合正电子寿命测量结果，观察到在掺Ｆｅ的半绝缘型ＩｎＰ中存在ＶＰ－Ｆｅ络合物     

LPMOVPE生长GaAs：C薄膜

本用低压金属有机气相外延技术和四溴化碳作为掺杂源生长重掺碳ＧａＡｓ：Ｃ．由于采用了较高衬底温度，ＧａＡｓ：Ｃ的空穴迁移率比相同空穴浓度条件下，用铍、锌等常用ｐ型掺杂原子生长的ＧａＡｓ高；中还分析了由于重掺碳引起的晶格收缩。     

有机金属气相外延GaAs的载流子浓度与外延气氛中As/Ga值的关系

OMV法非有意掺杂外延GaAs的载流子浓度受外延气氛中As/Ga值的控制。本研究中发现: As/Ga值等于十四左右, N型外延GaAs的迁移率有一个最大值,相应的载流子浓度较低。掺硫N型外延GaAs的载流子浓度随As/Ga值的增加而下降。 本文分析了OMV法的外延机构,提出了质量输运控制下的界面反应区部分反应热力学平衡模型,从而导出了Ⅵ族、Ⅱ族以及Ⅳ族元素的掺杂关系式。应用这些关系式能满意地解释OMV法外延GaAs的载流子浓度与As/Ga值的关系,并能说明其他工艺条件(外延温度、生长速率、掺杂量等)对外延GaAs载流子浓度的影响。 研究结果已经应用于GaAs FET材料的制备工艺,因而掺S外延GaAs的载流子浓度得到了有效的控制。     

1．55μm InGaAsP／InPDH激光器中的0．95μm发光带与Auger复合

报道了在１．５５μｍＩｎＧａＡｓＰ／ＩｎＰ激光器中发现的０．９５μｍ波长高能发光峰的一系列实验结果，并通过分析肯定了ＩｎＧａＡｓＰ有源区的Ａｕｓｅｒ复合是造成载流子向两侧ＩｎＰ限制层漏泄的主要原因，也是影响１．５５μｍＩｎＧａＡｓＰ／ＩｎＰＤＨ激光器Ｔ０值的主要因素。     

利用AFM电场诱导GaAs表面的局域氧化制备纳米结构

基于ＡＦＭ电场诱导的方法成功地在掺杂ｎ型ＧａＡｓ（１００）和锌掺杂ｐ型ＧａＡｓ（１００）表面局域氧化制备了纳米尺度的点、线、图形,最小的纳米结构约１５ｎｍ,并定性地考察了ＧａＡｓ表面ＡＦＭ电场诱导制备的纳米结构的一些规律。     

InGaAsP／InP异质结光电三极管的制备

介绍了ｎ－ＩｎＰ／ｐ－ＩｎＧａＡｓＰ／０－ＩｎＰ结构的异质结光电三极管制作过程，并获得了对１．３μｍ的入射光，光增益达２２０，用带尾纤的ＧａＡｓ／ＧａＡｌＡｓ发光管测量，光学增益达１４７０。     

激光触发光导开关产生超短电磁脉冲的实验研究

本文介绍了用光导开关和微带线结构产生电脉冲的实验装置，研究了激光能量和偏置电压对光导开关输出超短电脉冲的影响和三种尺寸光导开关的特性，测得了一种低掺杂Ｃｒ：ＧａＡｓ材料的载流子寿命约为１．８ｎｓ，显示了这种装置用作高速光探测器的可能性。     

InAs／GaAs低维结构中载流子快速俘获过程的研究

用简并激发－探测技术研究了７７Ｋ温度下ＩｎＡｓ／ＧａＡｓ量子点中载流子快速俘获和驰豫过程,在瞬态反射谱测量中,降观察到与ＧａＡｓ有关的驰豫过程外（时间常数约为１ｐｓ）,还观察到一个时间常数为几个至２０ｐｓ的反射率上升过程。提出了一个物理模型,表明上述上升过程与光致载流子被ＩｎＡｓ层快速俘获过程有关,并由此得到载流子的俘获时间,俘获时间随载流子浓度增加而减小。     

同质及异质外延生长InSb中可控的p型和n型掺杂

本文对在ＩｎＳｂ及ＧａＡｓ衬底上用分子束外延生长的ＩｎＳｂ分别以Ｂｅ和Ｓｉ作ｐ型和ｎ型的掺杂作了研究。当衬底温度超过３４０℃时，利用二次离子质谱技术，在ＩｎＳｂ衬底上生长时，发现Ｂｅ向表面有反常迁移现象。而在ＧａＡｓ衬底上生长的掺Ｂｅ的ＩｎＳｂ薄膜中未发现这种迁移。在掺Ｓｉ的ＩｎＳｂ膜中也未发现掺杂剂的再分布现象。ＩｎＳｂ中Ｂｅ的掺杂效率约是ＧａＡｓ中的一半，若想使Ｓｉ在ＩｎＳｂ中的掺杂效率达到其在ＧａＡｓ中的掺杂效率，在整个生长过程中，需将衬底温度维持在＜３４０℃。利用低温生长技术，可生长出呈现二维电子气体特性的Ｓｉ△－掺杂结构。     

掺施主杂质半导体中LO声子的反对称光电导响应的Monte Carlo模拟

本文基于一个伴随ＬＯ声子发射的光激发电子被重新俘获的物理模型，采用ＭｏｎｔｅＣａｒｌｏ方法，对掺施主杂质的半导体光电导谱中与ＬＯ声子相对应的反对称谱峰结构进行了理论模拟，并与Ｓｉ掺杂的ＧａＡｓ及ＩｎＰ的实验结果作了比较．     

Minority carrier diffusion length in liquid epitaxial GaP

Using a Schottky diode photocurrent technique, investigations have been made of the room temperature value of minority carrier diffusion length in liquid epitaxial GaP grown on both (111) and (100) oriented pulled GaP substrates. Results are presented for undoped layers and layers doped separately with S, S and N, Te, Zn, and Zn and O, to cover a range of impurity concentration in the GaP. The measured values of minority carrier diffusion length are found to depend on the concentration of the dominant impurity and, for the undoped and Zn doped layers, also on the growth orientation of the substrate. From the dependence of the minority carrier diffusion length on majority carrier concentration we infer the dominant room temperature recombination process in the layers. In our undoped layers this process is believed to correspond to recombination via residual Si substituted on P sites. In Te, S, Zn, and Zn, O doped layers the dominant recombination mechanism can be attributed to a non-radiative band-band Auger process, although in the case of the Zn, O doped layers a competing recombination process is observed which is believed to correspond to recombination via centres formed by unpaired O and Zn defects. The lifetime for this competing process is predicted to be sensitive to annealing.     

退火处理后非掺磷化铟的电传输特性

利用变温霍尔和电流-电压特性(I-V)两种方法分别对半导体和半绝缘的退火非掺磷化铟材料进行了测量.在非掺退火后的半导体磷化铟样品中可以测到缺陷带电导,这与自由电子浓度较低、有一定补偿度的原生非掺磷化铟的情况类似.非掺SI-InP表现出不同于原生掺铁的SI-InP的I-V特性,在一直到击穿为止的外加电场范围内呈欧姆特性,而掺铁SI-InP的I-V具有与陷阱填充有关非线性特征.根据空间电荷限制电流的理论,这种现象可以解释为非掺SI-InP中没有未被电子占据的空的深能级缺陷.     

退火处理后非掺磷化铟的电传输特性

利用变温霍尔和电流-电压特性(I-V)两种方法分别对半导体和半绝缘的退火非掺磷化铟材料进行了测量.在非掺退火后的半导体磷化铟样品中可以测到缺陷带电导,这与自由电子浓度较低、有一定补偿度的原生非掺磷化铟的情况类似.非掺SI-InP表现出不同于原生掺铁的SI-InP的I-V特性,在一直到击穿为止的外加电场范围内呈欧姆特性,而掺铁SI-InP的I-V具有与陷阱填充有关非线性特征.根据空间电荷限制电流的理论,这种现象可以解释为非掺SI-InP中没有未被电子占据的空的深能级缺陷.     

Effects of S,Si, or Fe dopants on the diffusion of Zn in InP during MOCVD

Diffusion of Zn in InP during growth of InP epitaxial layers has been investigated in layer structures consisting of Zn-InP epilayers grown on S-InP and Fe-InP substrates, and on undoped InP epilayers. The layers were grown by metalorganic chemical vapour deposition (MOCVD) atT = 625° C andP = 75 Torr. Dopant diffusion profiles were measured by secondary ion mass spectrometry (SIMS). At sufficiently high Zn doping levels ([Zn] ≥8 × 10¹⁷ cm⁻³) diffusion into S-InP substrates took place, with accumulation of Zn in the substrate at a concentration similar to [S]. Diffusion into undoped InP epilayers produced a diffusion tail at low [Zn] levels, probably associated with interstitial Zn diffusion. For diffusion into Fe-InP, this low level diffusion produced a region of constant Zn concentration at [Zn] ≈ 3 × 10¹⁶ cm⁻³, due to kick-out of the original Fe species from substitutional sites. We also investigated diffusion out of (Zn, Si) codoped InP epilayers grown on Fe-InP substates. The SIMS profiles were characterised by a sharp decrease in [Zn] at the epilayer-substrate interface; the magnitude of this decrease corresponded to that of the Si donor level in the epilayer. For [Si] ≫ [Zn] in the epilayer no Zn diffusion was observed; Hall measurements indicated that the donor and acceptor species in those samples were electrically active. All these results are consistent with the presence of donor-acceptor interactions in InP, resulting in the formation of ionised donor-acceptor pairs which are immobile, and do not contribute to the diffusion process.     

Effect of Doping and Excitation Wavelength on Charge Carrier Dynamics in Hematite by Time‐Resolved Microwave and Terahertz Photoconductivity

The charge carrier dynamics of epitaxial hematite films is studied by time‐resolved microwave (TRMC) and time‐resolved terahertz conductivity (TRTC). After excitation with above bandgap illumination, the TRTC signal decays within 3 ps, consistent with previous reports of charge carrier localization times in hematite. The TRMC measurements probe charge carrier dynamics at longer timescales, exhibiting biexponential decay with characteristic time constants of ≈20–50 ns and 1–2 μs. From the change in photoconductance, the effective carrier mobility is extracted, defined as the product of the charge carrier mobility and photogeneration yield, of differently doped (undoped, Ti, Sn, Zn) hematite films for excitation wavelengths of 355 and 532 nm. It is shown that, unlike in conventional semiconductors, donor doping of hematite dramatically increases the effective mobility of the photogenerated carriers. Furthermore, it is shown that all hematite films possess higher effective mobility for 355 nm excitation than for 532 nm excitation, although the time dependence of the photoconductance decay, or charge carrier lifetime, remains the same. These results provide an explanation for the wavelength dependent photoelectrochemical behavior of hematite photoelectrodes and suggest that an increase in photogeneration yield or charge carrier mobility is responsible for the improved performance at higher excitation energies.     

Reduction of dislocation densities in InP single crystals by the LEC method using thermal baffles

We have developed a modified liquid encapsulated Czochralski (LEC) method with thermal baffles, by which low dislocation density InP crystals can be grown. In this method, thermal baffles are set on top of the crucible in order to suppress the gas convection and thus to improve the temperature gradient in the LEC furnace. However, the dislocation densities depend not only on the temperature gradient but also on other growth conditions, such as crystal/crucible rotation rates, cooling rates, and the thickness of the pBN crucible. Since the rotation rate affects the solid/liquid interface shape, it is an important factor for the reduction of dislocation densities. By optimizing these conditions, for Sn and Fe doped InP crystals, average dislocation densities less than 5 x 10³ cm⁻² can be achieved. Dislocation free (DF) S and Zn doped InP crystals can also be grown if the carrier concentration is more than 3 x 1018 cm⁻³. The DF crystals become rectangular in shape.     

Compressively strained 1.3 μm InAsP/InP and GaInAsP/InP multiplequantum well lasers for high-speed parallel data transmission systems

Turn-on delay times in the pulse response of compressively strained InAsP/InP double-quantum-well (DOW) lasers and GaInAsP/InP multiple-quantum-well (MQW) lasers emitting at 1.3 μm were investigated. DQW lasers with 200-μm cavity length and high-reflection coating achieved both a very low threshold current (1.8 mA) and a small turn-on delay time (200 ps), even under a biasless 30-mA pulse current. Compressively strained or lattice-matched GaInAsP MQW lasers and GaInAsP double-heterostructure (DH) lasers were also fabricated and compared. It was observed that the carrier lifetime was enhanced for InAsP DQW lasers and strained GaInAsP MQW lasers compared to the lattice-matched GaInAsP MQW lasers and conventional double-heterostructure lasers. To explain this increase in the carrier lifetime, the effect of the carrier transport on the carrier lifetime was studied. The additional power penalty due to the laser turn-on delay was simulated and is discussed     

The minority carrier lifetime in doped and undoped p-type Hg0.78Cd0.22Te liquid phase epitaxy films

This paper will describe: (1) the first comparative study of recombination mechanisms between doped and undoped p-type Hg_1-xCd_xTe liquid phase epitaxy films with an x value of about 0.22, and (2) the first determination of τ_A7 ⁱ/τ_A1 ⁱ ratio by lifetime’s dependence on both carrier concentration and temperature. The doped films were either copper- or gold-doped with the carrier concentration ranging from 2 x 10¹⁵ to 1.5 x 10¹⁷ cm^-3, and the lifetime varied from 2 μs to 8 ns. The undoped (Hg-vacancy) films had a carrier concentration range between 3 x 10¹⁵ and 8 x 10¹⁶ cm^-3, and the lifetime changed from 150 to 3 ns. It was found that for the same carrier concentration, the doped films had lifetimes several times longer than those of the undoped films, limited mostly by Auger 7 and radiative recombination processes. The ineffectiveness of Shockley-Read-Hall (SRH) recombination process in the doped films was also demonstrated in lifetime vs temperature curves. The important ratio of intrinsic Auger 7 lifetime to intrinsic Auger 1 lifetime, τ_A7 ⁱ/τ_A1 ⁱ, was determined to be about 20 from fitting both concentration and temperature curves. The reduction of minority carrier lifetime in undoped films can be explained by an effective SRH recombination center associated with the Hg vacancy. Indeed, a donor-like SRH recombination center located at midgap (E_v+60 meV) with a capture cross section for minority carriers much larger than that for majority carriers was deduced from fitting lifetime vs temperature curves of undoped films.     

非掺杂InP中深陷阱与载流子的产生和输运的影响

利用四波混频(FWM)技术对未掺杂双面抛光的InP晶片进行了测试分析.室温下在1064nm用时间分辨皮秒四波混频技术测试了材料的载流子的产生、复合、衰减动力学以及曝光特性等过程.阐明了InP中深陷阱在载流子的产生与输运中的作用,并给予了解释.未掺杂InP样品的衍射效率作为能量函数可用两个光栅周期来表达.未掺杂InP样品中的深施主缺陷也由空间电荷载流子的输运过程来证实.     

闭管扩散Zn对InP表面性质的影响

利用闭管扩散方法以Zn3P2为扩散源，在不同扩散温度和扩散时间下对非故意掺杂InP (100）晶片进行扩散. 用电化学C-V法（ECV）和二次离子质谱法(SIMS)分别测出了空穴浓度和Zn的浓度随深度的分布曲线. 结果表明扩散后InP表面空穴和Zn的浓度在扩散结附近突然下降，InP表面空穴浓度主要取决于扩散温度，扩散深度随着扩散时间的增长而变大，InP表面Zn浓度一般比空穴浓度高一个数量级. 另外对扩散后的样品进行光致发光（PL) 测试，表明在保证表面载流子浓度的同时，适当降低扩散温度和增加扩散时间能减小对InP表面性质的影响.