Anisotropy in selective metalorganic vapor phase epitaxy of CdTe on GaAs and Si substrates

Abstract

CdTe epitaxial layers are grown by metalorganic vapor phase epitaxy (MOVPE) on patterned (100) Si and (100) GaAs substrates using SiO2, Si3N4 or CaF2 masks. Selective epitaxy of CdTe can be achieved by using Si3N4 and CaF2 masks and by controlling the growth conditions during MOVPE. The selectively grown CdTe layers show strong anisotropy depending on the orientation of the window pattern on the mask, as well as on the orientation of the starting substrates. CdTe with smooth atomically flat surfaces and vertical side walls can be obtained on (100) GaAs substrates by suitably orienting the window pattern directions and optimizing the growth conditions. For the growth conditions that are suitable for the selective growth, the growth is mass-transfer limited. The lateral growth rate depends on the ratio of the window width to the mask width. Use of CaF2 allows wider temperature window for selective growth since no nucleation was observed on CaF2 even at 450°C.