Effect of Flux Rate Variation at Fixed V/III Ratio on Semi-Polar (112¯2) GaN: Crystal Quality and Surface Morphology Study

Abstract

We report on the crystal improvement of semi-polar (112¯2) gallium nitride epitaxy layer on m-plane (101¯0) sapphire substrate by changing the flux rate at a fixed V/III ratio. The high-resolution X-ray diffraction (HR-XRD) analysis showed that lower flux rate enhanced the crystal quality of GaN epitaxy with the lowest FWHM values of 394 and 1173 arc seconds at [11¯23] and [11¯00] planes, respectively. In addition, Raman spectroscopy showed that flux rate did not affect the stress state of the GaN crystal. However, atomic force microscopy (AFM) micrograph depicted an anomalous trend where the lowest flux rate produces roughest surface with RMS roughness of 40.41 nm. Further analysis of AFM results on the undulation period length along [11¯23] and [11¯00] directions is carried out. It shows that as the growth rate decreases, the average undulation period along [11¯23] and [11¯00] directions increases from 2.59 µm and 1.90 µm to 3.52 µm and 3.52 µm, respectively. The mechanism for the surface roughening at the lower flux rate is then explained by using the adatom surface diffusion relation L ~ Dτ.

Non-Polar Gallium Nitride for Photodetection Applications: A Systematic Review

“…Hence, these investigations should be further implemented to further support the material quality and its correlation to the device performance. In other words, the screw dislocation and/or defects would have an impact on the surface, whereby these dislocations/defects could generate a tension tangential to the surface, leading to surface depressions that were prevailing on the surface [31,79,80,102].…”