Electronic and microstructural properties of disorder-induced gap states at compound semiconductor–insulator interfaces

Abstract

In order to clarify the structure and properties of the disordered semiconductor layer which forms the basis of the recently proposed disorder-induced gap state (DIGS) model, the electronic and microstructural properties of the compound semiconductor insulator–semiconductor interfaces (InP, GaAs, AlGaAs, InGaAs) are studied using C–V, isothermal capacitance transient spectroscopy, photocapacitance transient spectroscopy, cross-sectional transmission electron microscopy, Rutherford backscattering spectrometry, and x-ray and ultraviolet photoemission spectroscopy techniques. Based on the experimental results, a detailed model of the disordered layer which consists of a disordered crystal region and a graded amorphous region is presented. In these two regions, DIGS are distributed both in energy and space. The model can reproduce the observed hysteresis behavior remarkably well, and can explain the observed anomalous thermal and optical transient behavior. The measured location of the charge neutrality point EHO of DIGS continuum with respect to the valence-band maximum agrees well with the theoretical locations of the hybrid orbital energy based on sp3s* tight binding theory for various semiconductors.