Band bending at heterovalent interfaces: Hard X-ray photoelectron spectroscopy of GaP/Si(001) heterostructures

GaP is a preferred candidate for the transition between Si and heterogeneous III-V epilayers as it is nearly latticematched to Si. Here, we scrutinize the atomic structure and electronic properties of GaP/Si(0 0 1) heterointerfaces utilizing hard X-ray photoelectron spectroscopy (HAXPES). GaP(0 0 1) epitaxial films with thicknesses between 4 and 50 nm are prepared by metalorganic vapor phase epitaxy on either predominantly single-domain (SD) or two-domain (TD) Si(0 0 1) surfaces. The antiphase domain content in the GaP films is in situ controlled, employing reflection anisotropy spectroscopy. Via the analysis of core level photoelectron intensities, we reveal core level shifts of the P 2p and Si 2p peaks near the interface as well as core level shifts in the Ga 3d peaks near the surface. We suggest an Inter-Diffused Layer (IDL) model of the GaP/Si(0 0 1) interfacial structure with Si-P bonds at the heterointerface and residual P atoms in the Si substrate. Using a newly developed Parametrized Polynomial Function (PPF) approach, we derive a non-monotonic band bending profile in the heterostructures, correct experimental valence band offsets implying interfacial electronic barriers, and determine valence band discontinuities of Delta EV = 1.1 +/- 0.2 eV (SD samples) and Delta EV = 0.8 +/- 0.2 eV (TD samples) at GaP/Si(0 0 1) interfaces.