New buffer layer technique using underlying epitaxial AlN films for high-quality GaN growth

Abstract

We demonstrate high-quality epitaxial AlN films on C-plane sapphire as a new buffer layer technique for the growth of high-quality GaN. The obtained GaN films were atomically flat and the full width at half maximum (FWHM) values of the X-ray rocking curve (XRC) were 120arcsec and 510arcsec for (0004) and (10-10), respectively. XRC-FWHM values of the underlying AlN film were 90arcsec and 1800arcsec for (0004) and (10-10), respectively. The XRC results of the GaN indicated that tilted mosaicity of the GaN was much smaller than that of conventional GaN and that small tilted mosaicity coincided with small twisted mosaicity. It was characteristic that the twisted mosaicity drastically reduced from the AlN to the GaN. According to TEM results, it was clarified that the high-quality AlN layer had an effect in reducing the amount of screw-type threading dislocations and that the GaN/AlN interface played an important role in reducing the amount of edge-type dislocations.

Dislocation Reduction Mechanism in Low-Nucleation-Density GaN Growth Using AlN Templates

“…In type A, the GaN films were grown on conventional low-temperature GaN buffer layers. In type B, the GaN films were grown on the 1-mm-thick AlN layers grown directly (no buffer layer) on c-plane sapphire substrates, in a low-pressure MOCVD reactor, 7) using the same V/III flow ratio as that in type A.…”

“…Therefore, we investigated the relationship between the threading dislocation and island nucleation densities in type-A GaN growth with a large-tilt-angle distribution and in type-B GaN growth using an AlN-T with a high c-axis crystalline orientation. 7) Although the AlN-T has a high density of edge dislocations, it is known that low-dislocation-density GaN films with a high c-axis crystal orientation can be grown on this template.…”

Metalorganic Chemical Vapor Deposition and Material Characterization of Lattice-Matched InAlN/GaN Two-Dimensional Electron Gas Heterostructures

“…(0001) sapphire in a lowpressure MOCVD system (AIX 200/4 RF-S) using a hightemperature AlN buffer layer technique. 10) The InAlN/GaN heterostructure consists of, from bottom to top, a 2-m-thick highly-resistive GaN layer and an In 0:18 Al 0:82 N barrier layer with thickness ranging from 5 to 27 nm. For some samples, a 1-nm-thick AlN layer was inserted at the InAlN/GaN heterointerface under the expectation not only of enhancing 2DEG carrier confinement 7,11) but also of protecting the GaN surface during the growth interval.…”

Ultraviolet InAlGaN Light Emitting Diodes Grown on Hydride Vapor Phase Epitaxy AlGaN/Sapphire Templates

“…Most approaches utilize sapphire substrates combined with a high-temperature AlN base layer grown by metal organic chemical vapor deposition (MOCVD). [8][9][10][11][12][13][14][15][16][17] However, most UV LED heterostructures comprise AlGaN epi layers with AlN mole fractions in the range of 20 to 60%. Therefore, a closer lattice matched AlGaN base layer with a similar AlN mole fraction would be preferable.…”