Improvement of life time of minority carriers in GaAs epi-layer grown on Ge substrate

Abstract

A buffer layer structure on Ge substrate was studied for MOCVD growth of a high-quality GaAs layer. The buffer layer structure was designed taking into consideration both lattice constants and thermal expansion coefficients of GaAs and Ge. It consisted of a preliminarily grown thin layer of Al x Ga 1− x As and a GaAs layer. Photoluminescence (PL) decay of a GaAs layer in an Alo 0.2Ga 0.8As-GaAs-Al 0.2Ga 0.8As double-hetero (DH) structure, which was grown on the buffer layer structure, was observed by time-resolved PL method to estimate the quality of epilayers in the DH structure. The PL decay time strongly depended on Al content ( x) of the Al x Ga 1− x As preliminary layer, and the highest value was obtained when the x was 0.25. A PL decay time above 20 ns was successfully obtained for the DH structure grown on the buffer layer structure, which consisted of a 0.05 μm thick Al 0.25Ga 0.75As layer and a 1 μm thick GaAs layer. Although this value was half of that for the DH structure grown on GaAs substrate, it was much longer than the value of 3 ns for the DH structure grown on Ge substrate with a conventional GaAs buffer layer 1 μm thick.