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Light-Emitting Diode Fabrication
Published in Dave Birtalan, William Nunley, Optoelectronics, 2018
HVPE technology has been a successful technique employed to produce epitaxial material for commercial applications for many years. In the late 1960s, it was used to produce gallium arsenide phosphide, which was processed into red visible LEDs. These early diodes were used as digital displays in calculators, watches, and a variety of other applications.
Growth Technology for GaN and AlN Bulk Substrates and Templates
Published in Wengang (Wayne) Bi, Hao-chung (Henry) Kuo, Pei-Cheng Ku, Bo Shen, Handbook of GaN Semiconductor Materials and Devices, 2017
Michael Slomski, Lianghong Liu, John F. Muth, Tania Paskova
With the availability of larger wafers, produced by HVPE, the regrowth by HVPE was optimized and proven successful in maintaining the seed wafers size during the HVPE seeded growth.136 Even the very early HVPE regrowth on HVPE free-standing crystals showed that the material produced during regrowth possesses significantly improved structural characteristics. In particular, the dislocation density was found to be noticeably reduced. The analysis of the defect density in the regrown HVPE-GaN with different thicknesses has shown that the trend of decreasing the defect density with increasing thickness remains.137 The high purity of the crystals and the high optical quality have been proven reproducible. In particular, the low-temperature photoluminescence (PL) spectra of the regrown GaN films showed comparable narrow (~2 meV) exciton peaks as in the PL spectrum of the seed. However, based on different studies performed by variety of techniques, such as X-ray diffraction, PL, and Raman scattering spectroscopies,136,137 it is clear that both the residual strain and curvature (radius of about 10 m in the best case) of the seed was reproduced, which remains the main undesirable characteristics of these materials.
Effects of coating cycles on spin-coated indium nitride thin films
Published in Surface Engineering, 2018
Zhi Yin Lee, Sha Shiong Ng, Fong Kwong Yam, Zainuriah Hassan
Up to now, various advanced epitaxy deposition techniques have been employed to synthesise InN, including molecular beam epitaxy (MBE), metal-organic chemical vapour deposition (MOCVD), hydride vapour phase epitaxy, plasma-assisted reactive evaporation and reactive sputtering [8–10]. MOCVD is advantageous in producing large-area deposition, excellent composition control and film uniformity; however, the major problem with this method is the lack of availability of suitable precursors with sufficient volatility and stability. The crystallinity of InN is dependent on the V/III ratio, where In-droplet is observed at the decreasing source ratio [11]. On the other hand, MBE growth is dependent on the atomic species being deposited. To prevent atomic impurities, which may cause defects in the deposited thin films, an ultrahigh vacuum system is required to remove unwanted background gasses, such as oxygen. A high-quality thin film can be deposited through the aforementioned techniques; however, the set-up of the system is complicated and expensive [12,13]. Therefore, we proposed a relatively simple processing and cost-effective deposition technique, namely, sol–gel spin coating [14]. It is a dilute solution-based approach, which has been widely applied in producing doped and undoped metal oxide films (i.e. the oxides of tin, titanium and zinc). This is because of its capability to control film thickness and morphology [15–17]. A recent report showed that increasing the number of coating cycles has improved the crystallite size and photoluminescence emission intensity of a spin-coated oxide thin film [18]. To the best of our knowledge, few studies have reported on the growth of InN using sol–gel spin coating [19,20]; by contrast, the effect of the number of coating cycles on III-nitride thin films, especially InN, has not been investigated. Hence, we believe that the success of this study may contribute to the significant advancement of knowledge in materials science and thin film technology.