Fermi-level depinning and hole injection induced two-dimensional electron related radiative emissions from a forward biased Ni/Au-AlGaN/GaN Schottky diode

Electroluminescence (EL) from a forward biased Ni/Au-AlGaN/GaN Schottky diode was observed and studied. According to the EL spectra, which were dominated by the GaN near band edge emissions, holes were injected into the GaN layer. It was found that the turn-on voltage of the EL emission coincided with the second turn-on voltage that indicates the appearance of a second conduction channel in the diode's forward current-voltage characteristics. This coincidence implied that the second conduction channel originated from the hole injection. A model based on the Fermi-level depinning caused by the current induced interface states ionization is proposed to explain the hole injection process and the observed EL characteristics.