Direct Growth and Controlled Coalescence of Thick AlN Template on Micro-circle Patterned Si Substrate

Masafumi Jo,Shiro Toyoda,Norihiko Kamata,Noritoshi Maeda,Hideki Hirayama,Binh Tinh Tran

doi:10.1038/srep14734

Abstract

High-density micro-circle patterned Si substrates were successfully fabricated for the direct overgrowth of thick AlN templates by using NH3 pulsed-flow multilayer AlN growth and epitaxial lateral overgrowth techniques. The experimental results show that an 8-μm-thick AlN template was grown at a very high growth rate on the substrates. The AlN template had full widths at half maximum of 0.23° and 0.37° for the (002) and (102) reflection planes in X-ray diffraction rocking curves. Atomic force microscopy and transmission electron microscopy confirmed that the roughness of the surface was low (3.5 nm) and the dislocation density was very low (1.5 × 108 cm−2 (screw), 3.7 × 108 (edge) cm−2).

Highlights

AlGaN-based deep ultraviolet light-emitting diodes (UV-LEDs) have attracted considerable attention due to their wide range of applications in air and water purification, disinfection, chemical sensing, biomedicine, and non-line-of-sight communication[1,2]
We report the fabrication of micro-circle patterned Si substrates (mPSiS) and investigate thick AlN templates grown directly on these substrates for the first time
The samples were characterized by using X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) to determine the crystalline quality, surface roughness, thickness, and dislocation density, respectively

Summary

Introduction

AlGaN-based deep ultraviolet light-emitting diodes (UV-LEDs) have attracted considerable attention due to their wide range of applications in air and water purification, disinfection, chemical sensing, biomedicine, and non-line-of-sight communication[1,2]. AlGaN-based deep UV-LEDs require a thick, high-quality AlN template to be grown on the Si substrate before further AlGaN layers can be grown. Good-quality AlN templates are crucial for obtaining high-efficiency AlGaN-based deep UV-LEDs. there are many difficulties in growing a thick AlN template on Si substrates: the large lattice mismatch between AlN and Si(111) (~23.4%)[6] causes high dislocation density and crack initiating stress; the presence of the native oxide layer on the Si substrate leads to low coherence between the AlN template and the Si substrate[7,8]; AlN species with low mobility on the Si surface inhibit the structural rearrangement[9]; and the low growth rate, which is the main problem preventing the development of AlN films on Si and sapphire substrates. The samples were characterized by using X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) to determine the crystalline quality, surface roughness, thickness, and dislocation density, respectively

Methods

Results

Conclusion