Comparative study of GaAs epitaxial layers grown by MOCVD

The main aim of this work is to compare some galvanomagnetic and electrical properties, and also photoluminescence spectra of undoped GaAs epitaxial layers grown on (100) GaAs substrates by gas phase epitaxy using organometallic Ga source (OMVPE or MOCVD technique). It is hoped that the mentioned properties can show specific differcences. Preliminary results are presented here. Low temperature (at liquid He) photoluminescence spectra of undoped MOCVD GaAs layers of different origin (obtained from different laboratories) and of some undoped chloride VPE GaAs layers grown in our Institute have been compared. The layers grown on semi-insulating GaAs substrates have been characterized also both by C-V profilometry and Hall effect measurements. The photoluminescence intensity of the VPE layers is much greater compared to that of the MOCVD layers, though their surfaces were similarly treated. For the MOCVD samples it is characteristic that the exciton peaks seem to be donor bound exciton peaks, while the VPE samples indicate mainly acceptor bound excitons. The width of the acceptor related impurity peaks is wide in spectra obtained on OMVPE samples. Zn, Mg(Be) and C related peaks have been observed as typical ones.