Effects of different ions implantation on yellow luminescence from GaN

Abstract

The influence of C, N, O, Mg, Si and co-implants (Mg+Si) ions implantation with fluences in the wide range 10 13–10 17 cm −2 on the yellow luminescence (YL) properties of wurtzite GaN has been studied by photoluminescence (PL) spectroscopy. Two types of n-type GaN samples grown by metal-organic chemical vapor deposition method (MOCVD) and labeled as No-1 and No-2 were studied. In their as-grown states, No-1 samples had strong YL, while No-2 samples had weak YL. Results of the frontside and backside PL measurements in one of the as-grown GaN epifilms are also presented. Comparing the intensity of YL between frontside and backside PL spectra, the backside PL spectrum shows the more intense YL intensity. This implies that most of the intrinsic defects giving rise to YL exist mainly near the interface between the epilayer and buffer layer. Our experimental results show that the intensity ratio of YL to near-band-edge UV emission ( I YL/ I UV) decreases gradually by increasing the C implantation fluence from 10 13 to 10 16 cm −2 for No-1 samples after annealing at 900 °C. When the fluence is 10 17 cm −2, a distinct change of the I YL/ I UV is observed, which is strongly increased after annealing. For No-2 samples, after annealing the I YL/ I UV decreases gradually with increase in the C implantation fluence from 10 13 to 10 15 cm −2. The I YL/ I UV is gradually increased with increasing C fluence from 10 16 to 10 17 cm −2 after annealing, while I YL/ I UV for other ions-implanted GaN samples decreases monotonically with increase in the ions implantation fluences from 10 13 to 10 17 cm −2 for both No-1 samples and No-2 samples. It is noted that for annealed C-implanted No-2 samples I YL/ I UV is much higher than that of the as-grown one and other ion-implanted ones. In addition, I YL/ I UV for the Mg, Si, and co-implants (Mg+Si) implanted No-2 samples with a fluence of 10 13 cm −2 after being annealed at 900 °C is higher than that of the as-grown one. Based on our experimental data and literature results reported previously, the origins of the YL band have been discussed.