The solution of wetting issues in GaN epitaxy on (111) SCD with magnetron sputtered AlN

Abstract

Single crystal diamond (SCD) is an ideal heatsink for GaN-based devices. However, wetting issue of buffer on SCD hinders the GaN quality, limiting the full utilization of SCD's heat-dissipation ability. In this paper, the first-principles calculation revealed the high adsorption energy of Al and N adatoms on the surface of (111) SCD. The high energy of adatoms lead to a poor nucleation of AlN on (111) SCD, which caused inferior buffer layer. We propose a solution by pre-depositing AlN on (111) SCD via the ex-magnetron sputtering, which greatly enhances the quality of buffer layer and GaN film. Three different thicknesses of sputtered AlN (25 nm, 50 nm, and 100 nm were studied, and all showed improvement in GaN quality. The enhanced quality had been confirmed by the detailed characterization. GaN on (111) SCD with sputtered AlN presents narrower rocking curves of X-ray Diffraction (XRD). Additionally, GaN on 50 nm sputtered AlN/(111) SCD demonstrated superior quality, achieving a full width at half maximum of XRD for 1878/1945″ at 002/102.