Abstract
InP epitaxial layers grown by MOCVD on InP GaAs and GaAs/Si substrates have been studied using photoluminescence (PL) photoreflectance (PR) and electroreflectance (ER) at different temperatures. PL measurements at 300K indicated the intensity of the band-to-band transition to bear a ratio of 5. 4:1. 8:1. 1 in the sequence of InP/InP InP/GaAs and InP/GaAs/Si samples. At 10K the PL spectra showed four clear features. The full width at half maximum of the free exciton transition were 5. 4 8. 8 and 10 meV for the samples in the same sequence leading to a direct measure of the epilayer quality. The peak positions were the same between InP/InP and InP/GaAs but a 8. 4 meV shift towards the lower energy was seen with the InP/GaAs/Si sample indicating the influence of the large difference in thermal expansion coefficients. The intensity and width of the acceptor-to- donor signal was found to be quite different among the three samples and the relation to the diffusion length and surface electric field were examined. The PR data revealed the bandgaps to be 1. 334 1. 325 and 1. 294 eV for the InP epilayers on InP GaAs and GaAs/Si substrates respectively. A broad shoulder-like peak 30 meV below the fundamental absorption edge was observed only for InP/GaAs/Si and hence attributed to some shallow level defects induced by antiphase disorder. Temperature dependence showed different bandgap temperature coefficients and
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