Sapphire surface modified by a reactive ion beam for GaN depositions

The efficiencies and the lifetimes of GaN-based light-emitting diode and la ser diode can be improved by the proper choice of substrate or by the delib erate modification of the substrate surface before deposition. Buffer growt h or nitridation is the usual choice of surface modification for GaN deposi tion 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 temperatur e. The reactive ion-beam (RIB) pretreatment of sapphire results in a thin l ayer 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 p roperty. The present observation clearly demonstrates that the RIB pretreat ment of the sapphire surface can be used to improve the GaN films grown by metalorganic chemical-vapor deposition (MOCVD).