Improved Optical Quality of BAlGaN/AlN MQW Structure Grown on 6H-SiC Substrate by Controlling Residual Strain Using Mult
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Improved Optical Quality of BAlGaN/AlN MQW Structure Grown on 6H-SiC Substrate by Controlling Residual Strain Using Multi-Buffer Layer
Takayoshi Takano, Hideo Kawanishi, Makoto Kurimoto, Yoshiyuki Ishihara, Masato Horie and Jun Yamamoto Department of Electronic Engineering, Kohgakuin University, 2665-1 Nakano-machi, Hachiohji-shi, Tokyo 192-0015, Japan ABSTRACT BAlGaN and (BAlGaN/AlN) multi-quantum-wells (MQWs) structure were grown on 6H-SiC substrate by a low-pressure metalorganic vapor phase epitaxy (LP-MOVPE). Estimated boron compositions of the BAlGaN quantum wells by an Auger electron spectroscopy (AES) analysis were 0% to 13%. Photoluminescence (PL) spectra around 260 nm were observed at room temperature. The full-width at half maximum (FWHM) of PL spectra for BAlGaN/AlN MQW structure(with 2% of boron) was narrowed from 360 meV to 179 meV, as the residual strain in the BAlGaN well layer was decreased from 1.3% to 1.0% by increasing the Al content in the quantum wells.
INTRODUCTION Gallium nitride (GaN), aluminum nitride (AlN) and related materials have attracted special attention for application in light-emitting devices operating in the visible and deep ultraviolet spectral regions. Boron aluminum gallium nitride (BAlGaN) quaternary system can be lattice matched to 6H-SiC [1] and AlN substrates. The band-gap energy (Eg) of the BAlGaN with lattice matching to 6H-SiC is in the range of 3.8 eV (B0.017Ga0.983N) to 6.3 eV (B0.05Al0.95N), and the corresponding wavelength is in the range of 340 nm to 190 nm [2], respectively. Therefore, these systems are promising materials for use in the semiconductor lasers, which operate in the deep-UV spectral region. 6H-SiC and Al2O3 substrates are generally used for the epitaxial growth of nitride semiconductors. The advantages of the 6H-SiC substrate are not only lattice matching to the nitride semiconductor containing boron, but also its higher electrical conductivity than nitride grown on Al2O3 substrates, having the same cleavage facet face to GaN [1] and its high thermal conductivity. Some groups have studied for crystal growth of the BAlGaN system. Previously, BGaN ternary system has been grown by molecular beam epitaxy(MBE) [3] or LP-MOVPE [4,5]. The relationship between the band-gap energy and the boron composition for (BGaN/AlN) double heterostructures(DHs) has been experimentally determined [6]. Also band-gap energy and effective mass of the BGaN have been estimated [7]. On the other hand, the BAlN ternary has been grown by MOVPE [8]. The PL spectrum of BAlGaN, which was near the band-edge, has been observed from a low temperature (15 K) up to room temperature [6]. In this paper, UV photoluminescence (PL) of around 250-260 nm from the (BAlGaN/AlN) multi-quantum-well (MQW) structure is reported for the first time. And Composition of G12.9.1
BAlGaN epitaxial layer is also studied by an auger electron spectroscopy (AES) analysis. EXPERIMENT Figure 1 shows cross-sectional schematic diagrams of BAlGaN and (BAlGaN/AlN) MQW structures. On MQW structure, the BAlGaN and
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