Magnetophotoluminescence of MBE-grown InSb and InAs

Abstract

The magnetophotoluminescence from thin InSb layers grown by molecular beam epitaxy (MBE) on InSb and GaAs substrates and from MBE InAs on GaAs substrates is studied at low temperatures. With undoped homoepitaxial InSb, the photoluminescence (PL) spectrum contains up to five emission bands. From the observed magnetic field and excitation level dependence of the bands it is inferred that their origin is related to radiative recombination of an exciton-impurity complex, to direct recombination of a free electron with an uncharged acceptor, to recombination at an A+ centre and at deep defects. By comparison with PL from the substrate alone it is shown that two of the defects responsible are unique to the epilayer. The PL spectrum of epitaxial layers of InSb on GaAs shows a single broad band due to band-to-band radiative recombination in the InSb film. The PL of high-mobility InAs layers grown heteroepitaxially at 490 degrees C on GaAs shows a single emission line. Samples grown at lower temperature, resulting in lower mobility, show a second line due to direct recombination of a free electron with an uncharged shallow acceptor, suggesting a correlation between the reduction of mobility and the presence of this acceptor.