Exceptionally long GaN sub-micrometer rods grown by HVPE on a MOCVD-GaN rod template

Abstract

The growth mechanism of exceptionally long N-polar GaN sub-micrometer (sub-μm) rods has not been revealed to date. In this work, we investigated the effects of the V/III molar ratio and HCl (diluted in carrier gas) on the lengthening of a MOCVD-GaN rod template by HVPE. It is found that a low V/III molar ratio and HCl (diluted in carrier gas) help form vertical sidewalls and suppress the lateral growth on the top part of exceptionally long GaN sub-μm rods. Simulation results revealed that the low V/III molar ratio leads to reactive species distributing almost exclusively on the top part of GaN rods, which can effectively prevent crystal growth on the bottom of GaN rods. Chlorine ions support the growth by etching the sidewalls. After growth, the diameter and length of each GaN rod are more than 1.5 μm and 70–80 μm, respectively. Finally, an empirical growth model was developed to account for the exceptionally long GaN sub-μm rods under HVPE growth.