Fabrication of RF-ZnO buffer for epitaxial GaN layer on Si(111) substrate

Abstract

Satisfactory ZnO buffer has been fabricated through radio-frequency (RF) sputtering on Si(111) substrate. Ulteriorly, a low-temperature GaN (LT-GaN) interlayer growing on RF-ZnO/Si(111) can reduce the lattice mismatch and coefficient of thermal expansion mismatch between GaN epitaxial layer and Si(111) substrate. The optimal process conditions of RF-ZnO layer are as follows: background vacuum gets 6.0×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> Pa; sputtering power adopts 60W; pressure of Ar gas is 1.5Pa; heating temperature of Si(111) substrate is at 200°C. The RF-ZnO buffer has the unique (0002) crystal orientation, and the roughness of ZnO layer surface gets 1nm. The surface of GaN epitaxial layer grown on LT-GaN/Si(111) substrate is smooth and crack-free.