ScAlMgO₄: An Oxide Substrate for GaN Epitaxy

Abstract

We report the use of ScAlMgO4 as a substrate for the epitaxial growth of wurzitic GaN. The low misfit (+1.8%) allows coherent epitaxy of GaN, as observed by RHEED. The congruent melting of ScAlMgO4 makes Czochralski growth possible, suggesting that large, high quality substrates can be realized. Boules about 17mm in diameter are reported. We have used nitrogen-plasma molecular beam epitaxy to grow GaN epitaxial films onto ScAlMgO4 substrates. Band-gap photoluminescence has been observed from some of these films, depending primarily on the deposition conditions. A 3×3 superstructure has been observed by RHEED on the GaN surfaces. Structural analysis by x-ray diffraction indicates very good in-plane alignment of the GaN films. We also report thermal expansion measurements for ScAlMgO4.

Growth of Ga-face and N-face GaN films using ZnO Substrates

“…[10] An RF-coupled nitrogen plasma was used to obtain active nitrogen for MBE growth. The Ga flux was set to obtain a growth rate of 0.2µm/hr on sapphire substrates.…”

Epitaxial ScAlMgO4(0001) films grown on sapphire substrates by flux-mediated epitaxy

“…9 The BiO x flux was simultaneously supplied during the deposition by using a Bi-added SCAM target ͑SCAM: Bi =1:8͒. 4,10 The XRD scans of the film and substrate are shown in Fig. The substrate temperature and oxygen partial pressure were 700-900°C and 6 Torr, respectively.…”

Characterization of nitride thin films by electron backscatter diffraction

“…EBSD could be used, for example, to measure the orientation between nitride thin films and their substrates. Nitride thin films are predominantly grown on sapphire substrates with α‐SiC the next most common substrate, but thin films have been grown on MgO, ZnO, TiO 2 , LiAlO 2 , LiGaO 2 , MgAl 2 O 4 , InP, W, GaP and Si (Strite & Morkoç, 1992; Hellman et al. , 1996; Lee et al.…”