The characterization of defects, impurities, and carriers in gallium arsenide crystal growth and their effects on the electrical properties, thermal stability, and implant anneal characteristics

The concept of using various mapping techniques such as Near Infrared Transmittance Mapping (NIRT), growth striation photo etch and dislocation pit preferential etching are developed and used to characterize gallium arsenide (GaAs) crystal growth and the correlation to deep level donor imperfections (EL2), shallow dopant donor level, and dislocation formation in undoped Liquid Encapsulated Czochralski (LEC), silicon (Si) doped LEC, and Si doped Horizontal Bridgman (HB) grown crystals. The formation of carriers in undoped and Si doped LEC crystals is also studied using mapping techniques and electrical measurement (van der Pauw and Hall). The carrier formation in LEC undoped GaAs is the net balance of the contribution of EL2 deep donors and carbon acceptors. In Si doped LEC GaAs, the carrier formation is dominated by the compensation of electrons and holes generated from Si on gallium (Ga) and arsenic (As) sites respectively.; Photoconductivity is developed to characterize the p-type acceptor impurities, especially carbon acceptors in undoped LEC GaAs materials. The material thermal stability is found as a function of carbon acceptor content by photoconductivity measurement.; The thermally induced p-type surface conversion in LEC undoped GaAs materials is hypothesized to be multiple species diffusion process. The major species involved is the outdiffusion of EL2 during thermal treatment. Outdiffusion causes the EL2 concentration to fall below the background carbon acceptor concentration on the surface for high carbon content material and the material is converted to p-type on the surface. Other contributions are identified as indiffusion of surface sources of transition metals. These species may enhance material surface type conversion and degrade the n-type surface properties.; A thermal stability selection criterion for implantation applications is set up and verified as: the maximum tolerable depth of p-type conversion following annealing of un-implanted material is the depth of the intended implantation. The restriction of p-type conversion depth to less than the implantation depth optimizes the implant characteristics.