Grouped and Multistep Nanoheteroepitaxy: Toward High-Quality GaN on Quasi-Periodic Nano-Mask

Abstract

A novel nanoheteroepitaxy method, namely, the grouped and multistep nanoheteroepitaxy (GM-NHE), is proposed to attain a high-quality gallium nitride (GaN) epilayer by metal-organic vapor phase epitaxy. This method combines the effects of sub-100 nm nucleation and multistep lateral growth by using a low-cost but unique carbon nanotube mask, which consists of nanoscale growth windows with a quasi-periodic 2D fill factor. It is found that GM-NHE can facilely reduce threading dislocation density (TDD) and modulate residual stress on foreign substrate without any regrowth. As a result, high-quality GaN epilayer is produced with homogeneously low TDD of 4.51 × 10(7) cm(-2) and 2D-modulated stress, and the performance of the subsequent 410 nm near-ultraviolet light-emitting diode is greatly boosted. In this way, with the facile fabrication of nanomask and the one-off epitaxy procedure, GaN epilayer is prominently improved with the assistance of nanotechnology, which demonstrates great application potential for high-efficiency TDD-sensitive optoelectronic and electronic devices.

Efficient Dislocation Prevention and Thermal Transport Network Constructed by CNT Films on PSS for GaN-Based UV LEDs

“…A TEM test was performed on the cross-sectional GaN sample to demonstrate the threading dislocation (TD) blocking mechanism of the CNT network. Figure 2a,b shows the bright-field cross-sectional TEM images under the twobeam diffraction conditions with g = [0002] and [11][12][13][14][15][16][17][18][19][20]. Consistent with our SEM test result, high-density nanovoids that are related to GaN coalescence around CNTs can be observed.…”

“…This second selective area growth and dislocation blocking process is achieved by the chemical inaccessibility of CNTs, which grants CNT masks the ability to overcome the confinement of PSS and make a further reduction on TDD. It should be noticed that this blocking effect takes place at the 2D growth stage, indicating that subtle arrangement of CNT masks is less demanded . In contrast, a high fill factor mask, which can be achieved by CNTs with ease, is of greater importance to strengthen its blocking capability.…”

“…It should be noticed that this blocking effect takes place at the 2D growth stage, indicating that subtle arrangement of CNT masks is less demanded. 20 In contrast, a high fill factor mask, which can be achieved by CNTs with ease, is of greater importance to strengthen its blocking capability. The whole TDD reduction process is illustrated in Figure 2c.…”

“…In this work, a network combining functions of dislocation prevention and thermal transport is proposed and established by carbon nanotubes (CNTs) on PSS and contributes significantly to both TDD reduction and heat dissipation improvement in an economical way. A second selective growth process, or more specifically, a dislocation blocking process, is successfully introduced on the basis of PSS by cross-stacked CNTs, which has been proven effective in epilayer TDD reduction at an initial nucleation stage − and subsequent device performance improvements . Meanwhile, the high axial thermal conductivity of CNTs enables this network to uniform the temperature distribution and increase the thermal transport efficiency.…”

Enhanced Magneto-Optical Activities of Modulated Fe - Pt Multilayer Metamaterials

“…Short-range translational symmetry is broken in quasiperiodic systems [3,4] and quasicrystals [5]. In particular, patterned materials on the nanoscale with specific modulations that are based on quasiperiodicity show intriguing phenomena [6][7][8][9][10][11][12]. A plasmonic structure consisting of the modulated metallic and dielectric multilayers, for which the stacking sequences follow a Fibonacci series, demonstrated experimentally an enhancement of light-matter interaction [13].…”