Analysis of simultaneous occurrence of shallow surface Fermi level pinning and deep depletion in MOS diode with Mg-ion-implanted GaN before activation annealing

Abstract

The characteristics of a MOS diode with Mg-ion-implanted GaN before activation annealing were investigated. Mg ion implantation onto n-GaN with slightly high Si doping concentration (5 × 1017 cm–3) was performed with a moderate dosage (1.5 × 1012 cm–2). The completed MOS diode showed n-type features. The capacitance–voltage (C–V) and capacitance–frequency (C–f) characteristics of the MOS diode indicated that shallow surface Fermi level pinning and deep depletion occurred simultaneously. By applying the conductance method to the measured C–f characteristics, a discrete level at 0.2–0.3 eV below the conduction band edge was detected. On the basis of the simulation of the high-frequency-limit C–V curve, the detected discrete level distributed in the bulk of n-GaN rather than at the insulator/semiconductor interface, so that it caused surface Fermi level pinning at a relatively shallow energy level and deep depletion owing to its acceptorlike nature simultaneously.