High-Temperature Growth of GaN and Al x Ga1−x N via Ammonia-Based Metalorganic Molecular-Beam Epitaxy

Abstract

The effect of high-temperature growth on the crystalline quality and surface morphology of GaN and Al x Ga 1Àx N grown by ammonia-based metalorganic molecular-beam epitaxy (NH 3 -MOMBE) has been investigated as a means of producing atomically smooth films suitable for device structures. The effects of V/III ratio on the growth rate and surface morphology are described herein. The crystalline quality of both GaN and AlGaN was found to mimic that of the GaN templates, with (002) x-ray diffraction (XRD) full-widths at halfmaximum (FWHMs) of $350 arcsec. Nitrogen-rich growth conditions have been found to provide optimal surface morphologies with a root-mean-square (RMS) roughness of $0.8 nm, yet excessive N-rich environments have been found to reduce the growth rate and result in the formation of faceted surface pitting. AlGaN exhibits a decreased growth rate, as compared with GaN, due to increased N recombination as a result of the increased pyrolysis of NH 3 in the presence of Al. AlGaN films grown directly on GaN templates exhibited Pendellösung x-ray fringes, indicating an abrupt interface and a planar AlGaN film. AlGaN films grown for this study resulted in an optimal RMS roughness of $0.85 nm with visible atomic steps.

Towards high electron mobility in Gan(0001) based InGaN and AlGaN heterostructures

“…This was achieved by ammonia-MBE where active nitrogen is supplied by NH 3 . High ammonia overpressures resulted in the successful growth of GaN up to substrate temperatures of 950 °C [13]. The results were promising, but growth by this technique has its drawbacks.…”