Nearly perfect crystal growth of III–V compounds by the temperature difference method under controlled vapour pressure

Abstract

Nearly perfect crystals of III–V compounds are grown by a new LPE method which can produce homogeneous and high-quality crystals with controlled stoichiometry. Homogeneous epitaxial growth is performed at fixed temperature with a temperature difference in a melt, under controlled vapour pressure of the group V elements. In the experiment, the fluctuation of growing temperature is ascertained to produce a number of new defects and the effect of controlled vapour pressure is investigated. It has been ascertained that an optimum vapour pressure, which is the function of growing temperature, can suppress the generation of “rooty faults” to a minimum density. There is close agreement between the optimum vapour pressure in the heat treatment of crystals to reduce the generation density of lattice defects and the optimum vapour pressure to obtain defect-free crystals in the process of crystal growth. The epitaxial layers prepared under optimum vapour pressure have the highest mobility and the lowest additional carrier concentration. The lattice constant of the epitaxially grown crystal under controlled vapour pressure also shows a minimum value at optimum pressure. This also shows that the controlled vapour pressure is important in lattice fitting of epitaxial layers. The epitaxial layers grown by the temperature difference method (TDM) under optimum control of the vapour pressure (CVP) are almost as perfect crystallographically as measured by X-ray topography. The experiments are performed for GaP and GaAs.