Improved surface quality of solution grown GaAs and Pb 1−xSn xTe epitaxial layers: A new technique

Abstract

Factors which influence the surface quality of liquid epitaxial layers are discussed. The temperature gradient across the growth interface, the cooling rate, the growth temperature, and the melt thickness are all important since improper values can lead to constitutional supercooling. Several particular cases for GaAs are analyzed. The role of surface orientation in determining surface properties is also considered. For the NaCl lattice of Pb 1−x>Sn xTe the predicted preferred orientation for flat growth is {100}. For the zincblende lattice of GaAs the {111} and {100} orientations should produce the smoothest surfaces. A new growth apparatus with the growth substrate mounted on a cold finger in the furnace attains large, controllable temperature gradients across the growth interface while providing independent adjustment of all other important parameters. Nucleation studies of GaAs layers verify the dependence of surface quality on the imposed temperature gradient. There is almost no dependence of surface quality on substrate orientation for GaAs layers grown in a large temperature gradient. Nucleation studies of Pb 1−xSn xTe layers reveal a strong dependence of surface quality on both the imposed temperature gradient and the substrate orientation. The {100} orientation produces the smoothest layers.