Properties of radio-frequency-sputter-deposited GaN films in a nitrogen∕hydrogen mixed gas

Abstract

GaN films have been deposited by reactive sputtering in nitrogen gas at pressures from 0.08 to 2.70 Pa with and without the addition of hydrogen gas. X-ray diffraction (XRD), Fourier transform infrared (FTIR), optical absorption, and photoluminescence (PL) spectroscopy have been used to characterize the sputter-deposited GaN films. The XRD pattern reveals that the GaN films deposited in nitrogen gas at pressures lower than 0.53 Pa are polycrystals with the (0001) texture (α-GaN), while those deposited at or above 1.07 Pa display mixed crystalline orientations or an amorphous-like nature. The GaN:H films deposited in nitrogen∕hydrogen mixed gas, on the other hand, show an amorphous or amorphous-like nature. The FTIR spectra indicate that the GaN:H films show peaks arising from hydrogen-related bonds at ∼1000 and ∼3200cm−1, in addition to the GaN absorption band at ∼555cm−1. The optical absorption spectra at 300 K indicate the fundamental absorption edges at ∼3.38 and ∼3.7eV for the highly oriented α-GaN and amorphous GaN:H films, respectively. PL emission has been observed from sputter-deposited α-GaN films at temperatures below 100 K. The GaN:H films also show strong band-edge and donor-acceptor pair emissions. The PL emission in the GaN:H film may arise from crystalline GaN particles embedded in the amorphous GaN matrix.