High-quality GaN on AlN multiple intermediate layer with migration enhanced epitaxy by rf-molecular beam epitaxy

High-speed GaN growth of 1.0 mu m/h with migration enhanced epitaxy (MEE) b y molecular beam epitaxy using rf-plasma nitrogen (RF-MBE) was demonstrated . The electron mobility of MEE-GaN was 362 cm(2)/V.s for the electron densi ty of 1.7 x 10(17) cm(-3) at room temperature. The threading dislocation de nsity of MEE-GaN was estimated to be 1.0-3.0 x 10(10) cm(-2) based on the c ross-sectional transmission electron microscope (TEM) image. The remarkable improvement of electrical properties was obtained by the introduction of a high-temperature (750 degrees C) grown AIN/GaN multiple intermediate layer (AIN-MIL). The cross-sectional TEM image showed that threading dislocation s were bent or terminated at the AIN-MIL. The highest room temperature mobi lity of 668 cm(2)/V.s was obtained at the electron density of 9.5 x 10(16) cm(-3). The low-temperature peak mobility was 2340 cm(2)/V.s at 90 K.