Performance Improvement of AlN Crystal Quality Grown on Patterned Si(111) Substrate for Deep UV-LED Applications.

Binh Tinh Tran,Hideki Hirayama,Daishi Inoue,Noritoshi Maeda,Tomoka Kikitsu,Masafumi Jo

doi:10.1038/srep35681

Binh Tinh Tran, Hideki Hirayama + Show 4 more

Open Access

https://doi.org/10.1038/srep35681

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Abstract

An AlN template layer is required for growth of AlGaN-based deep ultraviolet light-emitting diodes (UV-LEDs). However, the crystal quality of AlN templates grown on both flat and patterned Si substrates has so far been insufficient for replacing templates grown on sapphire substrates. In this work, we grew a high-quality AlN template on 2 in. micro-circle-patterned Si substrate (mPSiS) with two different sizes and shapes through controlling the bias power of inductively coupled plasma (ICP) etching. The experimental results showed that the best AlN template was obtained on a large pattern size with a bow-angle shape and the template had X-ray rocking curves with full widths at half-maximum of 620 and 1141 arcsec for the (002) and (102) reflection planes. The threading dislocation density near surface of AlN template through transmission electron microscopy (TEM) estimation was in the order of 107 cm−2, which is the lowest dislocation density reported for a Si substrate to our knowledge. A strong single electroluminescence (EL) peak was also obtained for an AlGaN-based deep UV-LED grown on this template, means that it can be used for further developing high-efficiency deep UV-LEDs.

Highlights

In this letter, we report the fabrication of high-density micro-circle-patterned Si substrate (mPSiS) with different pattern sizes and shapes for comparison for further growth of thick AlN template
We report the fabrication of high-density mPSiS with different pattern sizes and shapes for comparison for further growth of thick AlN template
For the mPSiS etched with a bias of 10 W, the angle of the pattern sidewall and the ground was nearly perpendicular, mPSiS was etched with a bias of 5 W, the angle changed to 45°-bow and the pattern sizes were larger than those for mPSiS-A

Summary

Introduction

We report the fabrication of high-density mPSiS with different pattern sizes and shapes for comparison for further growth of thick AlN template. To grow thick AlN templates directly on the substrates, we use NH3 pulsed-flow multilayer AlN growth and ELO (epitaxial lateral overgrowth) techniques in a MOCVD reactor. The mPSiS fabrication is simpler, faster, and more effective than other methods, and the growth conditions are optimized with slight differences from previous report[19]. The AlN crystal quality effected by pattern sizes and shapes are mainly studied and evaluated by using X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), (TEM), and etch pit density (EPD) to determine the crystal quality, surface roughness, thickness, and dislocation density, respectively. An AlGaN-based deep UV-LED was grown on that template, carried out the EL measurement and compared with another AlGaN-based deep UV-LED which grown on a lower crystal quality AlN template to prove that the template is useful and it can be used to develop deep UV-LED devices with high quantum efficiency

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