Characterization of Electronic Structures of Deep Levels in Semiconductors by Magneto-Circular Emission Spectrum

(1)半导体中深层杂质电子结构的研究综述了半导体中深层杂质电子结构的实验和理论研究，特别提到了过渡原子杂质所引入的电子结构。(2)磁圆二色光谱测量仪的布置、设置与调整结合本资助项目购买的光学元件，构建了近红外磁圆二色光谱测量仪。该装置由卤钨光源、单色器、椭球镜光学系统、偏振器、压电双折射调制器、极片穿孔电磁铁、含氦低温恒温器、冰箱和用于红外探测的半导体光电池组成。该装置配备了一个电子系统，包括两个锁定放大器和一个基于微处理器的数据采集系统。该仪器能够测量0.4- 2.4um的MCD，磁场高达13kG，温度从20K到300K。(3)采用水平Bridgmann（HB）法制备不同浓度铬掺杂的半绝缘GaAs晶片、液相包封法生长的未掺杂半绝缘GaAs晶片、不同电导率类型（p、i、n）的无铟掺杂的无位错GaAs晶块和掺杂铁的掺杂铟掺杂的InP晶片作为MCD测量的样品进行切割和抛光。还进行了砷气氛热处理或铬扩散处理。(4) MCD谱的测量与理论分析所有测得的样品均显示出低于晶体本质基本能隙特征的MCD结构。其中，假设从自旋轨道分裂价带跃迁到与Cr相关的深态，利用量子缺陷模型分析了hb生长GaAs:Cr中与光离跃迁相关的MCD谱。计算谱与实验谱拟合较好，能量阈值为0.89eV，自旋轨道参数为0.2eV。后一个值与已知的价带分裂值相比太小；即0.35 ev。这表明有必要对理论进行修改。(5)MCD作为一种晶体评价技术，发现MCD光谱对结晶度非常敏感；例如，经过热处理，光谱形状发生了巨大的变化。因此，如果我们能够对不同处理的晶体的MCD数据进行分类，就可以清楚地表明，该技术可以作为晶体性质的评价方法。少

(1)Survery of electronic structures associated with the deep levels in semiconductorsExperimental and theoretical studies concerning the electronic structures of deep impurity levels in semiconductors were surveyed with particular reference to those introduced by transition atom impurities.(2)Layout, setup and abjusting of apparatus for magneto-circular dichroism spectrumBy combining optical elements purchased by this grant-in-aid, apparatus for the measurement of magneto-circular dichroism spectrum in the near-infrared region was constructed. This apparatus consists of a halogen-tungsten light source, a monochromator, an optical system with ellipsoidal mirrors, a polarizer, a piezo-birefringent modulator, an electromagnet with a perforation through its pole-pieces, a cryostat with helium a refrigerator and a semiconductor photocell for infrared detoction. This apparatus is equipped with an electronic system including two lockin-amplifiers and a microprocessorbased data-acquisition sys … More tem. This apparatus is capable of measuring the MCD for 0.4- 2.4um with magnetic field up to 13kG between temperatures from 20K to 300K.(3)Preparation of specimensChromium-doped semi-insulating GaAs wafers with different concentration of chromium made by the horizontai Bridgmann(HB)-method, an undoped semi-insulating GaAs wafer grown by liquid encapsulated Czochralski(LEC) technique, indium-doped dislocation-free GaAs ingots with different conductivity types(p,i,n) and LEC-grown InP wafers doped with iron were cut and polished to serve as specimens for the measurement of MCD. Heat treatment in arsemic atmosphere or chromium diffusion was also carried out.(4)Measurement and theoretical analysis of MCD spectraAll specimens measured showed MCD structures below the fundamental energy gap characteristic to the nature of the crystal. Among these spectra, MCD spectrum associated with the photoionization transition in HB-grown GaAs:Cr was analyzed in terms of the quantum defect model assuming the transition occurs from spin-orbit-split valence bands to Cr-related deep states. The calculated spectrum fit to the experimental one was satisfactory with the energy threshold 0.89eV and spin-orbit parameter of 0.2eV. The latter value is too small compared with that known for valence band splitting; i.e. 0.35eV. This suggests that a modification of the theory is necessary.(5)MCD as a crystal evaluation techniqueIt was found that MCD spectrum is very sensitive to crystallinity; for example the spectral shape changes drastically by heat treatment. Therefore, it becomes clear that the technique can be used as an evaluation method for crystal properties if we can classify MCD data for crystals with different treatments. Less