GaAs/AlGaAs quantum wells and double-heterostructure lasers grown by chemical beam epitaxy

Abstract

The growth system and growth kinetics of chemical beam epitaxy (CBE) are briefly described and its differences from molecular beam epitaxy (MBE) and organometallic chemical vapor deposition (OMCVD) are discussed. We characterize the capability of this technique in preparing high quality multilayer heterostructures by growing GaAsAl x Ga 1− x As single and multiquantum wells and double-heterostructure lasers. Studies using low-temperature photoluminescence and excitation spectroscopy techniques show that on the average the quantum wells are similar in quality to similar structures from the laboratory grown by MBE and in some important respects, superior to those grown by OMCVD. An interface roughness of δ L ≲± a/2, where a is the lattice constant, and very square wells (undistorted) even with continuous growth, in contrast to OMCVD, are inferred from the excitation spectra. Unusually sharp exciton transition peaks up to E 3h including forbidden transitions were obtained in single quantum wells. Such high quality lineshape has not been obtained in MBE- or OMCVD-grown wafers so far. The excitation spectra also show no evidence of band filling due to holes or electrons from the Al x Ga 1− x As layers which is a common problem with the OMCVD technique. From this study, it is also shown that the GaAs and Al x Ga 1− x As materials are of very high purity. The first GaAs/Al x Ga 1− x As double-heterostructure lasers grown by CBE is also achieved. Very low averaged current threshold densities of ≌ 500 A/cm 2 were obtained for wafers with active layer thicknesses of ∼ 500–1000 Åand confinement layers of Al 0.5Ga 0.5As. Such current threshold densities were similar to those obtained from the best wafers grown by other techniques. The present results unequivocally established that CBE is capable of producing high optical quality multi-layer heterostructures for state-of-the-art device applications.