Effect of low-temperature-grown GaN cap layer on reduced leakage current of GaN Schottky diodes

Abstract

In this study, GaN Schottky barrier diodes (SBDs) were grown by organometallic vapor phase epitaxy (OMVPE). It was found that we could significantly reduce reverse-bias leakage current by introducing a low-temperature-grown (LTG) GaN layer on top of the conventional GaN SBDs. The reduction has a factor of 3–4 in a typical GaN∕Ni∕Au SBD having LTG GaN cap layer. Atomic force microscopy showed that surface pits of threading dislocation (TD) termination did not almost observed as the LTG GaN cap layer was grown to be disposed on a typical high-temperature (HT) GaN layer. Therefore, this reduction in leakage current could be related to the reduction of surface pit densities of threading dislocation termination by using LTG GaN cap layers. This might be due to the suppression of surface states existing in the vicinity of TD terminations.