Contributions of ion-induced damage restoration and removal in GaN light emitting diodes

The reactive-ion etching method has been widely used for fabricating GaN based devices. However, ion-induced damage degrades the performance of the resultant devices. In this paper, using KOH and H₃PO₄:H₂O chemical solution treatments, the ohmic resistance of GaN LEDs can be improved by the removal of native oxide. However, the reverse current-voltage characteristics of the GaN LEDs are degraded because of the enlargement and the depth of the resulting hexagonal etched pits. Using thermal annealing above 700 °C, the reverse breakdown performance of the GaN LEDs can be improved by restoration of the ion-induced damage. However, at a temperature higher than 1000 °C, both the forward and reverse current-voltage characteristics of the GaN LEDs are degraded because of the decomposition of GaN and the loss of nitrogen.