Real-time characterization of III-V compound semiconductor epitaxy: application to '6.1' materials

Abstract

The antimonides are potentially highly useful materials for low-power electronic-device applications. However, unlike P and As the volatility of Sb is very low, comparable to that of Al and Ga. As a result surface stoichiometry during growth cannot be controlled simply by heating, which can result in defective material.

The objective of this work is to determine whether real-time optical diagnostics, specifically spectroscopic ellipsometry (SE) and reflectance-difference spectroscopy (RDS) can resolve this problem. We found SE to be essential, not only for reproducibly growing high-quality GaSb but also for obtaining new information about growth mechanisms. The SE data revealed that decomposition of the Sb precursor, trimethylantimony, was self-limiting in contrast to the Ga precursor, trimethylgallium. We also showed that laser light scattering (LLS) could provide the information necessary to optimize V/III flow ratios. This work represents the first uses of SE for real-time studies of antimonide growth and of LLS for real-time optimization of growth processes.

The SE data also showed the presence of crystalline GaSb during the earliest stages (first 10 s) of GaSb growth, revealing that the heteroepitaxial growth of GaSb on GaAs proceeds as a physical mixture of separate islands of GaAs and GaSb, in contrast to the expected mixing on the atomic-scale. All other post-deposition characterizations (AFM, SEM, XRD, TEM, and conductivity measurements) supported the information that the real-time optical data (SE, RDS, and LLS) revealed.