Sapphire surface modified by a reactive ion beam for GaN depositions

The efficiencies and the lifetimes of GaN-based light-emitting diode and laser diode can be improved by the proper choice of substrate or by the deliberate modification of the substrate surface before deposition. Buffer growth or nitridation is the usual choice of surface modification for GaN deposition to improve the crystal quality and properties. Reactive ion-beam (N ₂ ⁺) pretreatment of sapphire was carried out at room temperature to confirm the possibility of substituting the nitridation process at high temperature. The reactive ion-beam (RIB) pretreatment of sapphire results in a thin layer of an amorphous-like AlON-containing phase. The optical properties of GaN films deposited on RIB-treated sapphire vary, but GaN deposited on the smoothest surface modified by RIB preatreatment exhibits the best optical property. The present observation clearly demonstrates that the RIB pretreatment of the sapphire surface can be used to improve the GaN films grown by metalorganic chemical-vapor deposition (MOCVD).