Substratehyphen;induced peak in the photoluminescence of heavily doped epitaxial GaAs

摘要

A peak at 1.38 eV is observed in the 300hyphen;K photoluminescence ofn+andp+epitaxial GaAs. This peak appears as a shoulder of the principal bandhyphen;tohyphen;band emission. The shoulder is an artifact produced by the substrate and should not be interpreted as an additional optical transition. It is demonstrated that the subbandhyphen;gap luminescence, which arises from the bandhyphen;gap reduction caused by the heavy doping, travels through the transparent semihyphen;insulating substrate, reflects off the back surface, and is emitted from the epilayer. The shoulder intensity is enhanced by the scattering of light off the back surface. Thick substrates with polished back surfaces are optimum for reducing the shoulder peak.