PROPERTIES OF GAN EPILAYERS WITH VARIOUS GROWTH-CONDITIONS GROWN BY GAS-SOURCE MOLECULAR-BEAM EPITAXY

GaN epilayers on sapphire (0001) substrates were grown by the gas sour ce molecular beam epitaxy (GSMBE) method using ammonia (NH,) gas as th e nitrogen source. Properties of gallium nitride (GaN) epilayers grown under various growth conditions were investigated. The growth rate is up to 0.6 mu m/h in our experiments. Cathodoluminescence, photolumine scence and Hall measurements were used to characterize the films. It w as shown that the growth parameters have a significant influence on th e GaN properties. The yellow luminescence was enhanced at higher growt h temperature. And a blue emission which maybe related to defects or i mpurity was observed. Although the emission at 3.31 eV can be suppress ed by a low-temperature buffer layer, a high-quality GaN epilayer can be obtained without the buffer layer. (C) 1998 Elsevier Science B.V. A ll rights reserved.