MBE growth of GaN and AlGaN layers on Si(1 1 1) substrates: doping effects

Abstract

High-quality GaN layers with 8 arcmin (X-ray diffraction full-width at half-maximum, XRD FWHM) and rms surface roughness of 57 Å are grown on Si(1 1 1) substrates when using optimized AlN buffer layers. Si-doping produces n-type films reaching carrier concentrations up to 1.7×10 19 cm −3 with mobilities of 100 cm 2/V s. A reduction of the lattice parameter c together with a red shift in the photoluminescence (PL) emission is observed with increasing Si doping. The dislocation density observed by plan-view transmission electron microscopy (PVTEM) also decreases by close to one order of magnitude (from 5.3×10 9 to 8×10 8 cm −2) when increasing the Si doping (from 1.1×10 17 to 6.0×10 18 cm −3). AlGaN layers were grown with Al content ranging from 10% to 76% with XRD FWHM of 22 arcmin and intense low-temperature photoluminescence. N-type doping is achieved in AlGaN (40%) with Si, reaching electron concentrations of 8×10 19 cm −3.