Electrical, Luminescent and Structural Properties of Nanopillar GaN/InGaN Multi-Quantum-Well Structures Prepared by Dry Etching

Abstract

GaN/InGaN multiple quantum well (MQW) structures with undoped n-GaN cap imitating true light emitting diodes were grown on sapphire and converted to deep nanopillar (NP) structures by dry etching beyond the MQW region. Structural measurements, electrical measurements on Schottky diodes, microcathodoluminescence (MCL) spectra measurements indicate a strong relaxation of strain in NP MQWs manifested in the prominent increase of the bowing radius of the structures and in the blueshift of the MQW peak in MCL spectra. Various treatments of the as-etched NP MQWs (annealing at 700°C, etching in KOH, and soaking in (NH4)2S) progressively decreased the leakage current of Schottky diodes and increased the MQW MCL peak intensity due to the suppression of the dry-etching damage of the nanopillar sidewalls.

III‐Nitride Nanowires as Building Blocks for Advanced Light Emitting Diodes

“…For MQW GaN/InGaN blue LED structures with nanopillars created by dry etching one can clearly observe the decrease of strain manifested by high resolution X‐ray diffraction (HRXRD) maps and by a decrease in the bowing radius of the nanopillar sample compared to the starting planar sample. This decrease also results in the blue shift of the MQW luminescence peak because of the decrease of the magnitude of the QCSE field (see Figure (a,b)) . However, the MQW peak intensity immediately after RIE is lower than for planar structure because of the RIE‐related defects (Figure (b)).…”

“…As with nanopillars fabricated from single n‐GaN layers, additional removal of the surface damage regions from the nanopillars sidewalls by KOH solution etching had a beneficial effect on leakage current and MQW luminescence efficiency. Surface passivation of the nanopillar samples by soaking in (NH 4 ) 2 S led to some additional increase of the luminescence intensity and decrease of the leakage current, but also to a slight increase in strain caused by the presence of the sulfide layer on the surface and manifesting itself in some increase of the bending radius and some small red shift of the luminescence peak . It has to be noted that, even with all described after‐RIE treatments the leakage current of the nanopillar structures remains considerably higher than for the planar structure.…”

Investigation of water splitting using III‐N structures

“…The third group of samples (S3) were GaN/InGaN structures entirely grown by MOCVD with nano‐columns on the surface formed after the post‐growth processing . The as‐grown structure consisted (from the basal plane sapphire substrate upwards) of low temperature GaN nucleation layer, 1 μm undoped GaN buffer, 2 μm of Si doped n + ‐GaN, 5 periods of undoped GaN/InGaN quantum wells with the GaN barriers about 9 nm in thickness and InGaN QWs about 3 nm in thickness, with In composition around 12 mole% InN, and finally 120 nm of undoped n‐GaN cap.…”

Enabling Localized Surface Plasmon Emission from InGaN/GaN Nano-LEDs Integrated with Ag/SiO2 Nanoparticles

“…26 The etched GaN nanorod LEDs were vertically etched with 3 M KOH solution for 30 min to remove surface defects created during high-energy ion bombardment of plasma etching. 17 The residual SiO 2 etching masks were removed by immersing the sample in a buffered oxide etchant. In this manner, cylindrical blue InGaN/GaN nanorod arrays were obtained on the sapphire substrate, as depicted in the Supporting Information (Figure S1).…”

“…For improving the light extraction efficiency of nanorod LEDs, the study of the localized surface plasmon (LSP) effect is a topic of interest among several methods, such as physical surface passivation, chemical treatment, and strain relaxation. − The LSP coupling effect is recognized as a simple and effective approach to increase light extraction from nanorod LEDs. Here, free-electron oscillations occurring at the surface of metal nanoparticles (NPs) are responsible for the improvement in the light output of LEDs. − It is well-documented that strong LSP coupling is exerted between the active multiple quantum well (MQW) of LEDs and metal NPs with close proximity once the emission wavelength of LEDs matches the LSP resonance of metal NPs.…”