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

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 x 10(17) cm(-3)) was performed with a moderate dosage (1.5 x 10(12) 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 measuredC-fcharacteristics, 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-limitC-Vcurve, 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