A COMPACT VCE GROWTH SYSTEM FOR INSITU STUDIES OF EPITAXY

A vacuum chemical epitaxy (VCE) equipment for growing epitaxial layers of GaAs from triethylgallium (TEG) and arsine (AsH3) as precursors has been developed. A novel inlet system consisting of two separate concentric nozzle rings with sixfold symmetry has been designed. The directed molecular beams from the nozzles are redistributed by the wall of the growth chamber which is at a temperature of about 250°C, thus avoiding pre-reactions of metalorganic (MO) gases and the condensation of As-related species. In this manner a uniform molecule density, growth rate and a multiple impinging of volatile group-V species, typical for VCE, is realized. The changeable wall geometry also allows work under chemical beam epitaxy (CBE) like conditions. Grown layers of GaAs have been characterized using photoluminescence (PL), deep level transient spectroscopy (DLTS), carrier concentration profile measurements and morphology studies. In situ measurements were conducted with the aid of line-of-sight quadrupole mass spectrometry (QMS) and reflectance difference (RD) measurements. RD made it possible to characterize the growth process, and to optimize growth parameters such as the V/III ratio, also the pressure is too high for reflection high-energy electron diffraction (RHEED). We have specifically studied AsH3 and TEG stabilized surfaces, and the transitions between these two types of surfaces, in the temperature range between 400 and 550°C. © 1990.