Investigation and optimization of N-polar GaN porosification for regrowth of smooth hillocks-free GaN films

Abstract

This work investigates the process of planar electrochemical etching of pores in n-type nitrogen-polar GaN and the effect of pore morphology on regrown GaN film surface quality. An increase in the anodization voltage was found to increase the pore diameter and reduce the density of pores with inclined sidewalls near the surface of the porosified films. Simultaneously, a decrease in the hexagonal hillock size and number following GaN regrowth was observed. It is proposed that vertical pore sidewalls are essential to demonstrate high quality film coalescence. For smooth hillock-free 100 nm GaN regrowth, an optimal bias of 17 and 13 V for Ti-contacted N-polar GaN:Si with a Si doping of 4.5 × 1018 and 8 × 1018 cm−3, respectively, was found.

Demonstration of 82% relaxed In0.18Ga0.82N on porous GaN pseudo-substrate by plasma-assisted molecular beam epitaxy

“…They also reported the In x Ga 1-x N PS can exhibit elastic relaxation instead of the plastic relaxation observed in bulk In z Ga 1-z N regrowth by metal organic chemical vapor deposition (MOCVD) on relaxed In x Ga 1-x N on porous GaN PS [31][32][33]. Regrowth of MOCVD-grown InGaN on porous (In,Ga)N base layers was explored extensively in recent years [27,28,31,32,[34][35][36]. However, MOCVD growth of thick InGaN layers is challenging due to the high vapor pressure of nitrogen over InGaN and its low thermal stability.…”