In situ asymmetric island sidewall growth of high-quality semipolar (112̄2) GaN on m-plane sapphire

Abstract

In situ asymmetric island sidewall growth (AISG) was developed to enhance Ga-face facet growth and improve the crystalline quality of (1122) GaN epilayers on m-plane sapphire substrates. In the early growth stage island shaping and sidewall faceting were distinct and controlled by growth design. Using in situ AISG, {0002} instead of {1103} sidewall facets were formed on the Ga-rich island surface, which eliminated formation of a {1103} phase during subsequent layer growth of semipolar GaN. Enhanced Ga-face sidewall facet growth led to +c regions overlapping −c regions, which reduced defect density. Pure semipolar (1122) epilayers with a reduced surface striation density and a basal-plane stacking fault density of 8 × 10 3 cm −1 were obtained. The observation of a narrow E H 2 peak and an intense E 1 (LO) peak in Raman spectra indicates that almost strain-free high-quality semipolar (1122) GaN films were achieved. The photoluminescence emission intensity from the (1122) GaN film prepared by in situ AISG was dominated by band-edge emission and enhanced ∼4 times more than that from conventional (1122) GaN.

Semipolar (112¯2) GaN Films Improved by in situ SiNx Pretreatment of m‐Sapphire Substrate Surface

“…The presence of SiN x dielectric masks on sapphire substrate surface leads to the reduction of nucleated island density. As a result, the “generation” and/or “growth” of −c regions and coalescence boundaries with high‐density defects are suppressed by decrease of initially nucleated island density and by Ga‐richness enhanced +c‐sidewall facet growth . In summary, the crystalline quality and optical properties of the in situ SiN x pretreated sample B3 is significantly improved, which is evidenced by the XRD, Raman, and CL results.…”

“…Due to the lack of large‐sized and low‐priced () GaN bulk substrates, semipolar () GaN films grown on heterosubstrates have high‐density structural defects and rough surfaces, which have deleterious effects on the electrical and optical properties, reliability, and lifetime of the semipolar optoelectronic devices . Various methods such as two‐step growth, in situ asymmetric island sidewall growth, growth on patterned sapphire substrates (PSS), growth with incomplete interlayers, and epitaxial lateral overgrowth (ELO) have been employed to reduce the defect density in semipolar () GaN heteroepitaxial films. Unfortunately, the density of threading dislocations (TDs) and basal‐plane stacking faults (BSFs) remains very high in −c and window regions .…”

Impact of a Strained Periodic Multilayer on the Surface and Crystal Quality of a Semipolar (11–22) GaN Template

“…However, a few studies have proven that the utilization of simpler yet effective approaches would attain high-quality semipolar GaN. This includes the use of a double aluminum nitride (AlN) or GaN nucleation layer, 20 in situ thermal etching I-STEP technique, 21 nitride (SiN) interlayer, 22 indium nitride (InN) interlayer, 23 in situ asymmetric island sidewall growth (AISG) technique, 24,25 and graded superlattices of AlN/AlGaN as well as AlGaN/ AlGaN. 26 Despite the mentioned novel techniques, there is yet wellestablished research conducted in order to thoroughly investigate the use of AlN and GaN alternating multilayers (ML) for defect reduction in semipolar (11−22) on a planar m-plane.…”

“…However, a few studies have proven that the utilization of simpler yet effective approaches would attain high-quality semipolar GaN. This includes the use of a double aluminum nitride (AlN) or GaN nucleation layer, in situ thermal etching I-STEP technique, silicon nitride (SiN) interlayer, indium nitride (InN) interlayer, in situ asymmetric island sidewall growth (AISG) technique, , and graded superlattices of AlN/AlGaN as well as AlGaN/AlGaN …”

InGaN/GaN quantum well improved byin situSiNxpretreatment of GaN template

“…An indium posttreatment of InGaN epilayers was employed for selective etching of InGaN epilayers around threading dislocations, leading to a significant increase of light emission efficiency . Piezoelectric field (PF) within the InGaN/GaN QWs was usually eliminated/reduced by growth on nonpolar or semipolar atomic planes of GaN template . Energy band engineering by growth of complex InGaN/GaN QWs structures was also employed to reduce PF‐induced band bending and thus increase the internal quantum efficiency of InGaN/GaN QWs .…”