Parasitic behavior of different V/III ratios on the properties of InGaN/GaN heterostructures by MOCVD technique

Abstract

In this study, InGaN/GaN heterostructures were grown on a c-plane flat sapphire substrate (FSS) by using the metalorganic chemical vapor deposition (MOCVD) technique. The flow rates of the ammonia gas varied from 9 SLM to 24 SLM for the growth of InGaN thin film, which was equivalent to the V/III ratio of 6211–16562. Results indicated that a higher V/III ratio promotes parasitic behavior by hydrogen dissociated from ammonia. The parasitic behavior from hydrogen species etches the InN away from the growing surface and transforms the growth morphology from 3D islands to 2D growth mode. A slight reduction in indium composition was observed when increasing the V/III ratio. Next, more stable bandgap energy was observed for the InGaN thin films grown at higher V/III ratios. Improvements in electrical properties in terms of electron mobility and sheet resistance were observed at a higher V/III ratio which is associated with the improvement of crystalline quality and less defect density at a higher V/III ratio. The correlation of strain and carrier density of the thin films was further discussed. It was concluded that the growth of high crystalline quality and thick InGaN thin film was possible for solar cell applications at higher V/III ratio growth conditions.