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

Abstract

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 2.1eV and 0.3eV 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 (e1–hh1) transition blue-shifts by about 60meV for InAs0.38P0.62/InP SQW when the top InP barrier layer thickness is decreased from 22Å to 11Å. The experimental values of e1–hh1 electronic transition in SQW match well with those of the theoretically calculated ones using a 3.6eV potential barrier at the InP surface.