Band discontinuities in gallium phosphide/crystalline silicon heterojunctions studied by internal photoemission

We measured the band lineup of gallium phosphide (GaP) on crystalline silicon (c-Si) heterojunctions (HJs) by using internal photoemission (IPE), where the heterojunctions were prepared by using solid-source molecular beam epitaxy. It was found that the conduction-band and valence-band discontinuities, denoted by Delta E(c) and Delta E(v), are 0.09 +/- 0.01 and 1.05 +/- 0.01 eV, respectively. By performing measurements on samples with different GaP layer thicknesses, we clarified that Delta E(v) of the present GaP-on-Si HJs is not affected by strain normal to the growth direction. The values of Delta E(c) and Delta E(v) obtained for the GaP-on-Si HJs are significantly different from those reported for thin Si-on-GaP HJs, and the implications of this discrepancy are briefly discussed. (C) 2008 The Japan Society of Applied Physics.