Superlattices and Microstructures

Photoreflectance, Raman scattering, photoluminescence and transmission electron microscopy of MOCVD GaAs GaAlAs multiple quantum wells

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We have performed a systematic study of photoreflectance (PR), Raman scattering (RS), low temperature photoluminescence (PL) and transmission electron microscopy (TEM) on quantum wells (MQWs) grown by metal-organic chemical vapor deposition (MOCVD) with nominal well (LZ)/barrier (LB) widths of 100A/100A and 200A/200A. The large number of features observed in the PR spectra at 135K and 77K, combined with a theoretical calculation using the Bastard model enable us to characterize the structure of the MQWs, i.e., LZ, LB and barrier height. The values of LZ and LB height agrees with the Raman determination. In contrast with the theoretical calculation, the fundamental heavy-hole valence to conduction subband transitions in both samples occur at somewhat higher energies in both PR and PL. This apparent discrepancy suggests that the GaAs wells have been contaminated by about 1% mole fraction of Al. This is confirmed by the RS results and is also indicated by the growth conditions. © 1988.