Band bendings, band offsets, and interface instabilities inp+-GaAs/n−-ZnSe heterojunctions

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Abstract
The band bendings at the heterojunction interface between heavily doped p-type GaAs substrates and lightly doped n-type ZnSe epitaxial layers were studied with electric-field-induced Raman scattering by longitudinal-optical phonons. Molecular-beam epitaxy was used to deposit the ZnSe layers. The band bendings were determined as functions of sample temperature and time elapsed after formation of the junctions for different thicknesses of nominally conductive and nonconductive ZnSe layers. These determinations yielded insight into the ability of the Fermi level to respond at the interface according to various heterostructure parameters and external perturbations and allowed an estimation of the band offsets. A temporal evolution of the band bendings with time constants on the order of several days after formation of the junctions was detected. This effect is attributed to instabilities of the GaAs/ZnSe interface due to atomic exchange.