Disordering and anomalous surface erosion of GaN during ion bombardment at elevated temperatures

Abstract

Ion-produced lattice disorder—often an undesirable effect of ion implantation—can be reduced if implantation is carried out at an elevated temperature. We present here a study of the structural characteristics of wurtzite GaN bombarded with ¹⁹⁷Au⁺ ions at 550 °C over a wide dose range. Results show that disorder buildup and amorphization are suppressed at elevated temperatures, as compared to implantation at room temperature and below. With increasing ion dose, the evolution of damage proceeds via the formation of point-defect complexes and some planar defects, which are parallel to the basal plane of the GaN film. However, high-dose ion bombardment of GaN at elevated temperatures is complicated by anomalous surface erosion. Such an erosion is attributed to a three-step process of (i) the accumulation of implantation disorder with increasing ion dose, (ii) thermally and ion-beam-induced decomposition of a heavily damaged near-surface layer, and (iii) ion-beam-stimulated erosion of such a highly N-deficient layer.