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.

Study on growth and characterization of ScAlMgO4 substrate crystal

“…The interlayer forces are weaker than bond intensions; hence ScAlMgO 4 has a cleavage habit along the (0 0 0 1) plane. Moreover, the thermal expansion coefficient along the c-axis is about twice that of the aaxis in the ScAlMgO 4 , those being 12.2 × 10 −6 and 6.2 × 10 −6 • C −1 , respectively [12]. Temperature gradient and huge difference of the expansion/contraction property between a-and c-axis could provoke crystal to produce thermal stress.…”

MOVPE growth of AlGaN/GaN superlattices on ZnO substrates for green emitter applications

“…However, it is also found that high growth temperature will cause surface reaction. A diffraction peak at 37.41 was observed from the sample ZC can be identified as Ga 2 ZnO 4 , formed by the reaction between Ga and ZnO substrate at high growth temperature [13]. The growth temperature must be chosen with these two factors in mind, with too low a growth temperature leading to poor quality material and too high a temperature causing reactions at the GaN/ZnO interface.…”

InGaN growth with various InN mole fractions on m-plane ZnO substrate by metalorganic vapor phase epitaxy

“…that for the epilayers with a high InN mole fraction. This result may be due to the stronger reaction between the epilayer and ZnO [10], and further improvement of the growth technique is required to achieve an atomically smooth surface. Fig.…”