Insights into MOCVD process control as revealed by laser interferometry

In-situ laser interferometry has been used to study the nucleation of CdTe on basal plane sapphire in MOCVD growth. The nucleation delay and nucleatio n thickness were seen to be influential in the determination of overall buf fer layer quality. This nucleation process was seen to be highly complex an d the nucleation delay and nucleation layer thickness were seen to vary for constant conditions of nucleation II:VI ratio and temperature. A possible link between nucleation delay and nucleation temperature has been commented on. The results for CdTe on sapphire suggest that for consistent metalorga nic chemical vapor deposition (MOCVD) growth conditions from run to run dur ing the nucleation stage, the nucleation delay and thickness may still vary as a function of subtle differences in the substrate growth surface. This argument is further substantiated by our observations using laser interfero metry to study the nucleation of CdTe on Si (211)in MOCVD, where different surface preparatory treatments were employed. Laser interferometry was foun d to be sensitive to differences in surface treatment of the Si substrates prior to ZnTe/CdTe growth. The benefits of the use of interferometry to stu dy and to control the nature of complex epitaxial systems is discussed.