Band alignment and quantum states of InAsxP1-x/InP surface quantum wells investigated from ultraviolet photoelectron spectroscopy and photoluminescence

The band alignment and the quantum states of InAsxP1-x/InP surface quantum well (SQW) are investigated using ultraviolet photoelectron spectroscopy (UPS) and photoluminescence techniques. The analysis of UPS spectra of core levels In 4d, As 3d, P 3p and P 2p confirms that the top surface of. InAsxP1-x/Inp SQW contains an admixture of oxides, which convert into a more stable form of oxide, In(PO3)(3), after optimum Ar+ ion sputtering. The values of valence band offsets between In(PO3)(3)/InP and InAsxP1-x/InP (x=0.57) SQW are 2.1 eV and 0.3 eV respectively, as obtained from the onsets of UPS spectra. Further, the band structure of InAsxP1-x/InP SQW is also estimated from the UPS spectra of core levels and the valence band onsets after optimum Ar+ ion sputtering. The emission of the quantum states (e(1)-hh(1)) transition blue-shifts by about 60 meV for InAs0.38P0.62/InP SQW when the top InP barrier layer thickness is decreased from 22 angstrom to 11 angstrom. The experimental values of e(1)-hh(1) electronic transition in SQW match well with those of the theoretically calculated ones using a 3.6 eV potential barrier at the InP surface. (C) 2012 Elsevier B.V. All rights reserved.