Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 9, Issue 49, Pages 43386-43392Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.7b14801
Keywords
GaN; facet-controlled; epitaxial lateral overgrowth; sputtered AIN; patterned sapphire substrate; MOCVD
Funding
- National Natural Science Foundation of China [11304048, 61604045]
- Guangdong Academy of Sciences [2017GDASCX-0845]
- Science and Technology Program of Guangdong [2014TQ01C707, 2015B010132004, 2015B010134001, 2016B070701023]
- Pearl River S&T Nova Program of Guangzhou [201610010142]
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It is widely believed that the lack of high-quality GaN wafers severely hinders the progress in GaN-based devices, especially for defect-sensitive devices. Here, low-cost AIN buffer layers were sputtered on cone-shaped patterned sapphire substrates (PSSs) to obtain high-quality GaN epilayers. Without any mask or regrowth, facet-controlled epitaxial lateral overgrowth was realized by metal-organic chemical vapor deposition. The uniform coating of the sputtered AIN buffer layer and the optimized multiple modulation guaranteed high growth selectivity and uniformity of the GaN epilayer. As a result, an extremely smooth surface was achieved with an average roughness of 0.17 nm over 3 X 3 mu m(2). It was found that the sputtered AIN buffer layer could significantly suppress dislocations on the cones. Moreover, the optimized three-dimensional growth process could effectively promote dislocation bending. Therefore, the threading dislocation density (TDD) of the GaN epilayer was reduced to 4.6 x 10(7) cm(-2), which is about an order of magnitude lower than the case of two-step GaN on the PSS. In addition, contamination and crack in the light-emitting diode fabricated on the obtained GaN were also effectively suppressed by using the sputtered AIN buffer layer. All of these advantages led to a high output power of 116 mW at 500 mA with an emission wavelength of 375 nm. This simple, yet effective growth technique is believed to have great application prospects in high-performance TDD-sensitive optoelectronic and electronic devices.
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