Crystal anomaly at the center of S doped InP wafers grown by the LEC method

Crystal quality of 2′ Φ S doped InP substrates grown by the conventional liquid encapsulated Czochralski method was studied by the photoluminescence mapping technique and double crystal x-ray diffraction method. Dark currents of InGaAs/InP PIN-photodiodes (PIN-PDs) fabricated on them showed the existence of an anomaly at the center of the substrate. Photoluminescence intensity abruptly decreased at the center of the substrate. An abnormal curvature of the lattice plane was found at the center of the substrate by the double crystal x-ray diffraction measurement. We discuss the correlation between crystal quality of the substrate and dark currents of PIN-PDs.     

6-in diameter InP single crystals grown by the hot-wall LEC method and the mirror wafers

6-in diameter Fe-doped semi-insulating InP single crystals have been grown by the hot-wall liquid encapsulated Czochralski method. This method has a quartz inner vessel to stabilize the thermal convection. Temperature gradient and solid-liquid interface shape can be controlled by a multizone heater system. The weight of grown crystal was 18 kg and the full length was 250 mm. The dislocation density was about 1/spl times/10/sup 5/ cm/sup -2/. The resistivity was more than 1/spl times/10/sup 7/ /spl Omega/cm and its uniformity was the same as the smaller diameter crystal. The conditions of wafer processing were optimized to improve the wafer flatness. The rolloff and the slope of the wafer surface could be reduced especially by the improvement of the polishing conditions. The typical total thickness variation was 3.3 /spl mu/m, and it was comparable to the GaAs wafer.     

非掺及掺铁磷化铟中的残留施主缺陷

用辉光放电质谱(GDMS)测量了原生液封直拉(LEC)磷化铟(InP)的杂质含量.利用霍尔效应测到的非掺LEC-InP的自由电子浓度明显高于净施主杂质的浓度.在非掺和掺铁InP中都可以用红外吸收谱测到浓度很高的一个氢-铟空位复合体施主缺陷.这个施主的浓度随着电离的铁受主Fe2+浓度的增加而增加.这些结果表明半绝缘体中氢-铟空位复合体施主缺陷的存在对铁掺杂浓度和电学补偿都有重要影响.     

非掺及掺铁磷化铟中的残留施主缺陷

用辉光放电质谱(GDMS)测量了原生液封直拉(LEC)磷化铟(InP)的杂质含量.利用霍尔效应测到的非掺LEC-InP的自由电子浓度明显高于净施主杂质的浓度.在非掺和掺铁InP中都可以用红外吸收谱测到浓度很高的一个氢-铟空位复合体施主缺陷.这个施主的浓度随着电离的铁受主Fe2+浓度的增加而增加.这些结果表明半绝缘体中氢-铟空位复合体施主缺陷的存在对铁掺杂浓度和电学补偿都有重要影响.     

Dislocation profiles in HgCdTe(100) on GaAs(100) grown by metalorganic chemical vapor deposition

We studied dislocation etch pit density (EPD) profiles in HgCdTe(lOO) layers grown on GaAs(lOO) by metalorganic chemical vapor deposition. Dislocation profiles in HgCdTe(lll)B and HgCdTe(lOO) layers differ as follows: Misfit dislocations in HgCdTe(lll)B layers are concentrated near the HgCdTe/CdTe interfaces because of slip planes parallel to the interfaces. Away from the HgCdTe/CdTe interface, the HgCdTe(111)B dislocation density remains almost constant. In HgCdTe(lOO) layers, however, the dislocations propagate monotonically to the surface and the dislocation density decreases gradually as dislocations are incorporated with increasing HgCdTe(lOO) layer thicknesses. The dislocation reduction was small in HgCdTe(lOO) layers more than 10 μm from the HgCdTe/CdTe interface. The CdTe(lOO) buffer thickness and dislocation density were similarly related. Since dislocations glide to accommodate the lattice distortion and this movement increases the probability of dislocation incorporation, incorporation proceeds in limited regions from each interface where the lattice distortion and strain are sufficient. We obtained the minimum EPD in HgCdTe(100) of 1 to 3 x 10⁶ cm^-2 by growing both the epitaxial layers more than 8 μm thick.     

Modeling of the electron distribution in AlGaAs/GaAs (δ-Si) structures grown on vicinal surfaces

The potential and electron density distributions in AlGaAs/GaAs (δ-Si) structures grown on vicinal surfaces are calculated. It is shown that a lateral superlattice can form in the structures. The optimal technological parameters for obtaining a superlattice are estimated. Fiz. Tekh. Poluprovodn. 33, 1229–1231 (October 1999)     

"神舟3号"上生长Cd1-xZnxTe晶片Zn组分分布的显微荧光研究

用显微荧光(μ-PL)方法对在我国"神舟3号"上空间生长的CdznTe晶片中zn组分分布的研究.对晶片的单晶"壳"区及未完全熔化的"芯"区中的小结晶区域进行了逐点PL测量.对测得每一点的PL谱进行了拟合,得到测量点的禁带宽度参数Eg,其分布对应于CdznTe中zn的组分分布.测量结果给出了空间生长晶片zn组分布的变化趋势和统计规律.作为比较,测量并分析了一块采用相同方法在地面生长的CdznTe晶片.     

Optical properties of silicon-doped (100) GaAs layers grown by molecular-beam epitaxy

The photoluminescence spectra of (100) GaAs layers, both undoped and doped with silicon, is investigated at T=77 K. It is found that along with the B-band, which corresponds to interband radiative recombination, the spectra of doped layers also exhibit a so-called Si-band located near hν⋍1.4 eV. In multilayer δ-doped structures, an additional band appears in the region hν⋍1.47–1.48 eV, which is called here the δ-band. The dependence of the energy positions, intensities, and shapes of these photoluminescence bands on the doping dose N _Si, laser excitation power, and temperature are investigated. It is shown that the Si-band is caused by optical transitions between the conduction band and a deep acceptor level (∼100 meV) connected with Si atoms on As sites. It is also established that the dependences of the shape and intensity of the δ-band on temperature and photoluminescence excitation power are identical to the corresponding dependences for the B-band. The behavior of the δ-band in the photoluminescence spectra is viewed as evidence of quantum-well effects in the δ-doped structures. Fiz. Tekh. Poluprovodn. 32, 1060–1063 (September 1998)     

Raman scattering study of the immiscible region in InGaAsP grown by LPE on (100) and (111) GaAs

We have studied the asymmetric broadening of the Raman spectra of In_xGa_1-xAs_yP_1-y grown on GaAs substrates by means of the spatial correlation model. The broadening phenomena was found to be enhanced in the region of immiscibility, in agreement with PL observations. In Raman measurements, the broadening is more enhanced in the samples grown on (100) substrates than in the samples grown on (111) substrates. The enhancement is attributed to the immiscibility included in the samples grown on (100) substrate.     

STUDY OF MORPHOLOGICAL DISTRIBUTION OF DEFECTS IN GaAs WAFERS BY INFRARED DIGITAL IMAGE PROCESSING

A new method is applied to characterize the defects in GaAs material(e.g.the absorption ofEL2 centres).The method consists of transmitting a laser beam(λ=1.1-1.5μm)through the GaAs wa-fer of 4—8 mm thickness and 50 mm diameter.The image is received by the TOSHIBA 8844 cameraand entered into the DATASUD computer image processing system.This image is displayed on amonitor permitting to observe the inhomogeneity(like cross,cells and volutes)of theEL2 and dislocation defects.This paper will introduce a specific image processing software for GaAs materi-al,called ZHIMAG(ZHang IMAGe)and its application to GaAs wafer.The software can bealso applied to any other types of image processing.     

Electrical properties of ZnSe/GaAs (100) heterostructures grown by photostimulated vapor-phase epitaxy

Epitaxial layers of ZnSe were grown on GaAs (100) by photostimulated vapor-phase epitaxy, using a He-Cd laser (power P⋍1 mW/cm², hν=2.807 eV) at a substrate temperature of T= (175–300) K. The temperature dependences of the mobility of the majority charge carriers were studied in layers doped during growth, using such sources as AlCl₃, Zn, Al, and Ga. Based on an analysis of the thermally stimulated current and thermally stimulated depolarization curves, parameters were established for seven deep local levels that have a substantial effect on the electrical characteristics of the heterostructures. Fiz. Tekh. Poluprovodn. 31, 11–14 (January 1997)     

Imaging of the lateral GOI-defect distribution in silicon MOS wafers with lock-in IR-thermography

Yield and reliability of MOS devices are strongly affected by crystal-originated particles which may generate gate oxide integrity (GOI) defects. For the semiconductor industry it is highly desirable not only to measure the density, but also to image the lateral distribution of GOI-defects. A novel technique to image GOI defects across large gate areas has been developed. First, a low-ohmic bias pulse is used to break down nearly all GOI defects in a large-area MOS structure. Then a periodic bias of typically 2 V is applied and the local temperature variation caused by the leakage current through the broken GOI defects is imaged by lock-in IR-thermography. This technique has been used to image the GOI defect distribution across 8′′ Czochralski wafers. Various lateral variations of the defect distribution have been confirmed.     

硅片键合界面缺陷分布与Weibull模数的关系

从理论推导分析了键合片的缺陷分布与Weibull模数m之间的关系。此关系与实验相符,并利用此关系很好地解释了硅片键合强度随退火温度变化的关系。     

Features of the electric-field distribution in anisotropic semiconductor wafers in a transverse magnetic field

A macroscopic model of the Hall effects and magnetoresistance in anisotropic semiconductor wafers is developed. The results obtained by solving the electrodynamic boundary problem allow the potential and eddy currents in anisotropic semiconductors to be calculated at different current-contact locations, depending on the parameters of the sample material’s anisotropy. The results of this study are of great practical importance for investigating the physical properties of anisotropic semiconductors and simulating the electron-transport phenomena in devices based on anisotropic semiconductors.     

Photoreflectance characterisation of GaAs and GaAs/GaAIAs structures grown by MOCVD

Epitaxial undoped and doped (Si and Zn) GaAs and GaAIAs layers as well as heterostructures of GaAs/GaAIAs have been grown in an atmospheric pressure, vertical MOCVD system. Room temperature photoreflectance (PR) has been applied to characterise the layers and heterostructures as well as multiple quantum wells. The surface- and interface-related PR has been studied by application of Kramers–Kronig analysis. A decomposition of the PR spectrum into spectra connected with the surface region and with the interface has been proposed.     

Strain effects in CdTe (111) epitaxial layers grown on GaAs (100) substrates by molecular beam epitaxy

Spectroscopic ellipsometry and photoreflectance measurements on CdTe/GaAs strained heterostructures grown by moleculclr beam epitaxy were carried out to investigate the effect of the strain and the dependence of the lattice parameter on the CdTe epitaxial layer thicknesses. Compressive strains exist in CdTe layers thinner than 2 μm. As the strain increases, the value of the critical-point energy shift increases linearly. These results indicate that the strains in the CdTe layers grown on GaAs substrates are strongly dependent on the CdTe layer thickness. Author to whom all correspondence should be addressed.     

Photoluminescence investigation of Si-doped GaAs grown by molecular beam epitaxy on non-(100) oriented surfaces

The photoluminescence of Si-doped GaAs grown by molecular beam epitaxy on non-(100) oriented surfaces will be presented and reviewed. Particular care will be paid to show how photoluminescence can help the understanding of the behaviour of the dopants, unwanted impurities and point defects in differently oriented samples. Low temperature continuous-wave and time resolved luminescence data will be presented of (100), (111)A, (111)B, (211)A., (311)A, (311)B and (110) oriented samples with different doping levels.     

Investigation of distribution and redistribution of silicon in thin doped gallium-arsenide layers grown by molecular beam epitaxy on substrates with (100), (111)Ga, and (111)As orientations

The distribution of silicon in GaAs was investigated by secondary-ion mass spectrometry (SIMS) before and after the thermal annealing of thin doped GaAs layers grown by molecular beam epitaxy on substrates with (100), (111)Ga, and (111)As orientations. The surface relief pattern of the grown epitaxial films was studied by atomic-force microscopy both inside and outside the ion-etching crater developed during the SIMS analysis. Features of the surface relief inside the crater are revealed for various orientations. Changes observed in the shape of doping profiles are explained both by the features of the development of the surface relief during the ion etching accompanying the SIMS analysis and by an accelerated diffusion of Si over the growth defects.     

Analysis of CZT crystals and detectors grown in russia and the ukraine by high-pressure bridgman methods

Sandia National Laboratories (SNL) is leading an effort to evaluate vertical high pressure Bridgman (VHPB) Cd_1−xZn_xTe (CZT) crystals grown in the former Soviet Union (FSU) (Ukraine and Russia), in order to study the parameters limiting the crystal quality and the radiation detector performance. The stoichiometry of the CZT crystals, with 0.04<x<0.25, has been determined by methods such as proton-induced x-ray emission (PIXE), x-ray diffraction (XRD), microprobe analysis and laser ablation ICP mass spectroscopy (LA-ICP/MS). Other methods such as triaxial double crystal x-ray diffraction (TADXRD), infrared transmission spectroscopy (IR), atomic force microscopy (AFM), thermoelectric emission spectroscopy (TEES) and laser induced transient charge technique (TCT) were also used to evaluate the material properties. We have measured the zinc distribution in a CZT ingot along the axial direction and also its homogeneity. The (Cd+Zn)/Te average ratio measured on the Ukraine crystals was 1.2, compared to the ratio of 0.9–1.06 on the Russian ingots. The IR transmission showed highly decorated grain boundaries with precipitates and hollow bubbles. Microprobe elemental analysis and LA-ICP/MS showed carbon precipitates in the CZT bulk and carbon deposits along grain boundaries. The higher concentration of impurities and the imperfect crystallinity lead to shorter electron and hole lifetimes in the range of 0.5–2 and 0.1 μs, respectively, compared to 3–20 and 1–7 μs measured on U.S. spectrometer grade CZT detectors. These results are consistent with the lower resistivity and worse crystalline perfection of these crystals, compared to U.S.-grown CZT. However, recently grown CZT from FSU exhibited better detector performance and good response to alpha particles.