Formation of large-area GaN nanostructures with controlled geometry and morphology using top-down fabrication scheme

Abstract

This paper details the fabrication of GaN nanoscale structures using deep ultraviolet lithography and inductively coupled plasma (ICP) etching techniques. The authors controlled the geometry (dimensions and shape) and surface morphology of such nanoscale structures through selection of etching parameters. The authors compared seven different chlorine-based etch chemistries: Cl2, Ar, Cl2/N2, Cl2/Ar, Cl2/N2/Ar, Cl2/H2/Ar, and Cl2/He/Ar. The authors found that nitrogen plays a significant role in fabricating high quality etched GaN nanostructures. This paper presents the effects of varying the etch parameters, including gas chemistry, gas flow rate, ICP power, rf power, chamber pressure, and substrate temperature, on the etch characteristics, including etch rate, sidewall angle, anisotropy, mask erosion, and surface roughness. Dominant etch mechanisms in relation to the observed characteristics of the etched features are discussed. Utilizing such methods, the authors demonstrated the fabrication of nanoscale structures with designed shapes and dimensions over large area. Nanocolumns with diameter of 120 nm and height of 1.6 μm with sidewall angle of 86° (90° represent a vertical sidewall) were fabricated. Nanocones with tip diameter of 30 nm and height of 1.6 μm with sidewall angle of 70° were demonstrated. Such structures could potentially be used in light-emitting diodes, laser diodes, photodetectors, vertical transistors, field emitters, and photovoltaic devices. This study indicates the feasibility of top-down methods in the fabrication of next-generation nitride-based nanoscale devices, with large-area uniformity and scalability.

Facet recovery and light emission from GaN/InGaN/GaN core-shell structures grown by metal organic vapour phase epitaxy on etched GaN nanorod arrays

“…21,22 For core-shell arrays, the curanisotropic etch process can create nanorods from a planar template. 14,15 This has the benefit of delivering greater uni-rent path in the active region is in the radial direction and parallel to the axis within the core and outer shell. Similar formity at the expense of (1) possibly introducing etchfabrication approaches as for axial current devices can be related roughness and damage, and (2) being limited by the used provided that special attention is paid to the core and quality of the original planar template.…”

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

“…Successful producing the etching mask by standard submicron photolithography has been demonstrated in several papers (see e.g., refs. ). The main problems here are, of course, tight control over the etch rate, verticality, depth and diameter of nanowires, accounting for variations in the etch rates of doping and composition, the ability to produce structures of large area.…”

“…Etching in KOH‐based solutions was found to be conducive to obtaining the smooth defectless morphology and improving the verticality. Almost ideally nonpolar sidewalls could be obtained that way . The consequences are the appearance of shallow and deep level defects at the surface causing band bending and excessive surface leakage current, electron and holes capture by deep states leading to increased surface recombination velocity and to nonradiative recombination via deep traps.…”

Enhanced luminescence from GaN nanopillar arrays fabricated using a top-down process

“…al. [15,18] have reported a comprehensive study on the fabrication of GaN NPs and the influence of various etching parameters such as gas chemistry, ICP/RF power, chamber pressure and substrate temperature on the NP morphology. There are also some reports on enhancement in PL emission intensity from GaN NP arrays compared to that from an epilayer [19][20][21].…”