Energy distribution of interface state density in AlN/ n-GaAs heterostructures formed by laser chemical vapor deposition

Abstract

AlN/ n-GaAs heterointerface formed by the Laser Chemical Vapor Deposition techniques have been studied by the quasistatic-low-frequency and Terman's-high-frequency methods. The results compare favourably with those obtained from high-low frequency, conductance and DLTS methods. All of these methods give essentially the same results with interface trap densities in the range of 10 12–10 13 eV −1 cm −2 with a “U”-shaped energy distribution having a minimum at about E c − 0.9 eV. The distribution is analyzed in terms of exponential density-of-state tails derived from conduction and valence band edges in the Disorder Induced Gap State (DIGS) model. The surface Fermi level is pinned at E c − 0.83 eV by the requirement that depletion and interface charges are equal and opposite, and the charge distribution profile makes this pinned value particularly stable. The surface potential V s can be moved at most 0.35 eV either side of the pinned level before breakdown occurs in the AlN dielectric film.