Deposition of AlGaN films on (111) Si substrates and optimization of GaN growth on Si using intermediate-temperature AlGaN buffer layers

Al_xGa_1-xN films having various Al-contents were grown on (111) Si substrates over a temperature range of 800∼1000 °C. It was found that crack free Al_xGa_1-xN films were achieved when the films were grown at 800 °C. High temperature (HT) GaN films were also deposited on (111) Si substrates using 800 °C grown Al_xGa _1-xN buffer layers with different thickness and composition combinations. The best HT GaN film was achieved on (111) Si substrate by process optimization with an 800 °C grown 180 nm-thick Al_0.58Ga _0.42N buffer layer. Room temperature photoluminescence (PL) spectrum of the HT GaN film shows a strong near band edge emission having a linewidth of 100 meV and a quenched yellow luminescence. It is believed that the use of intermediate temperature Al_xGa_1-xN buffer layer is beneficial to accommodate the misfit strain between HT GaN film and (111) Si substrate.