Effect of double AlN buffer layer on the qualities of GaN films grown by radio-frequency molecular beam epitaxy

Abstract

This paper reports that the GaN thin films with Ga-polarity and high quality were grown by radio-frequency molecular beam epitaxy on sapphire (0001) substrate with a double AlN buffer layer. The buffer layer consists of a high-temperature (HT) AlN layer and a low-temperature (LT) AlN layer grown at 800 • C and 600 • C, respectively. It is demonstrated that the HT-AlN layer can result in the growth of GaN epilayer in Ga-polarity and the LT-AlN layer is helpful for the improvement of the epilayer quality. It is observed that the carrier mobility of the GaN epilayer increases from 458 to 858 cm 2 /V•s at room temperature when the thickness of LT-AlN layer varies from 0 to 20 nm. The full width at half maximum of x-ray rocking curves also demonstrates a substantial improvement in the quality of GaN epilayers by the utilization of LT-AlN layer.

Effect of nucleation layer morphology on crystal quality, surface morphology and electrical properties of AlGaN/GaN heterostructures

“…A two-step growth process utilizing a low temperature (LT) nucleation layer prior to high temperature (HT) GaN growth was established as the first breakthrough in obtaining device-quality smooth films. The role of the LT-nucleation layer has been widely studied and is now regarded as providing nucleation sites and controlling polarity in the subsequently deposited GaN layers [6] .…”