Effect of reactor pressure on the electrical and structural properties of InN epilayers grown by high-pressure chemical vapor deposition

Abstract

The influence of super-atmospheric reactor pressures (2.5–18.5 bar) on the electrical and structural properties of InN epilayers deposited on GaN/sapphire (0001) templates by high-pressure chemical vapor deposition has been studied. The epilayers were analyzed by Raman, x-ray diffraction (XRD), and Fourier transform infrared reflectance spectrometry to determine the structural properties as well as the phonon frequencies, dielectric function, plasma frequency, layer thickness and damping parameters of the epilayers. For the studied process parameter space, best material properties were achieved at a reactor pressure of 12.5 bar and a group-V/III ratio of 2500 with a free carrier concentration of 1.5 × 1018 cm−3, a mobility of the bulk InN layer of 270 cm2 V−1 s−1, and a Raman (E2 high) FWHM value of 10.3 cm−1. This study shows that the crystalline layer properties—probed by XRD 2θ–ω scans—improve with increasing reactor pressure.