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Defect Engineering in Heteroepitaxial Layers
Published in John E. Ayers, Heteroepitaxy of Semiconductors, 2018
Tsai et al.69 produced free-standing GaN films with EPDs less than 4 × 104 cm−2. In this work, a 2-μm-thick GaN template layer was first grown on a sapphire (0001) substrate by MOVPE. Next, a thick layer (50 to 200 μm) of GaN was grown on the template by HVPE. The resulting thick film of GaN was next separated from its sapphire substrate using laser-induced lift-off. Finally, an additional thickness of GaN was grown by HVPE. For the characterization of template layers and free-standing films, H3PO4:H2SO4 was used as the crystallographic etch, and the resulting etch pits were observed by AFM. In 2-μm-thick MOVPE template layers, the EPDs were found to be as high as 6 × 108 cm−2. In a 500-μm-thick free-standing GaN film, however, no etch pits were observed in the 50 μm × 50 μm field of view, therefore placing an upper limit of 4 × 104 cm−2 on the EPD.
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
HVPE is an attractive technique for bulk GaN growth due to its ability to produce thick layers of high quality with high growth rates and relatively low cost. The thick layers produced by HVPE can be used as quasi-bulk substrates after delamination, or to obtain GaN boules which can be sliced into GaN substrates. Nearly all of the GaN substrates in today’s market are fabricated by the HVPE technique, owing to its favorable processing conditions. Atmospheric pressure and relatively low processing temperature as compared to other techniques create a cost-effective growth method when paired with its high growth rate above 100 µm/h.78 The HVPE technique is able to obtain these high growth rates due to its high surface migration rates for the halide species.
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.
Impact of neutron irradiation on electronic carrier transport properties in Ga2O3 and comparison with proton irradiation effects
Published in Radiation Effects and Defects in Solids, 2023
Jonathan Lee, Andrew C. Silverman, Elena Flitsiyan, Minghan Xian, Fan Ren, S. J. Pearton
We used two different device structures as platforms for study of radiation effects, namely vertical rectifiers and lateral field effect transistors (FETs). The fabrication sequence for the Schottky rectifiers began with a layer structure of 10 m Si-doped (3.5 × 1016 cm−3) epitaxial layer grown by Halide Vapor Epitaxy (HVPE) on an (001) oriented 650 m -phase Sn-doped (n = 3.6 × 1018 cm−3) Ga2O3 substrate (Novel Crystal Technology). A full area backside Ohmic contact (20 nm / 80 nm, Ti / Au) was deposited by electron beam evaporation and annealed for 30 s at 550°C in N2 in a rapid thermal annealer. To form a field plate, 40 nm Al2O3 and 360 nm SiNx dielectric were deposited using Atomic Layer Deposition and Plasma Enhanced Chemical Vapor Deposition respectively. Windows with 100 m diameter were opened using 1:10 diluted Buffered Oxide Etchant (BOE). The sample surface was then treated in O3 for 20 min to remove contamination species including hydrocarbons. 400 m Ni/Au (80 nm/320 nm) Schottky metal was subsequently deposited using electron beam evaporation with standard acetone lift-off.
High reactivity of H2O vapor on GaN surfaces
Published in Science and Technology of Advanced Materials, 2022
Masatomo Sumiya, Masato Sumita, Yasutaka Tsuda, Tetsuya Sakamoto, Liwen Sang, Yoshitomo Harada, Akitaka Yoshigoe
The samples were +c, −c, and m-GaN bulks with polished surface grown by halide vapor phase epitaxy (HVPE), and +c- and m-GaN films grown by metalorganic chemical vapor deposition (MOCVD). XPS measurements were carried out at BL23SU, SPring-8 [6]. High-purity O2, N2O and NO gases diluted with 1% in helium gas were supplied through a nozzle head (φ100 μm) heated at approximately 1400 K. These gases were so pure that no impurity was detected by quadrupole mass spectrometer (QMS). We measured the gas concentration ratio of diluted oxidation gas by QMS, and the flux number listed in Table 1 was estimated according to the previous report [7]. This oxidation condition using O2 gas was mild enough to oxidize two monolayers of a Si surface in two hours of irradiation [8]. Since the molecular beam was not applied to H2O vapor, it was introduced at room temperature to keep the pressure in the XPS chamber at the same level of ~1 × 10−5 Pa corresponding to the same flux of the case of O2 gas. The O 1 s core spectrum was continuously detected with one scan for about 30 s at a binding energy of 538 to 525 eV until the end of irradiation. The details of the experiment were described elsewhere [5].
Low temperature processed CO2 laser-assisted RF-sputtered GaN thin film for wide bandgap semiconductors
Published in Journal of Asian Ceramic Societies, 2023
Seoung-Hyoun Kim, Chang-Hyeon Jo, Min-Sung Bae, Masaya Ichimura, Jung-Hyuk Koh
For GaN materials, single crystals or epitaxial thin films are difficult to prepare. Therefore, heteroepitaxial wafers are typically prepared using hydride vapor phase epitaxy (HVPE), metal–organic chemical vapor deposition (MOCVD), or molecular beam epitaxy (MBE) processes on GaAs heterogeneous substrates. To deposit a GaN epitaxial thin film on a single-crystal substrate, HVPE and MOCVD are typically employed. However, owing to the toxicity of CVD precursors, physical vapor deposition (PVD) processes are preferred for growing GaN thin films [8–10]. In Table 1, the different processes for preparing GaN thin films are summarized. As presented in the table, an extremely high substrate temperature surpassing 500°C is typically required to grow GaN thin films using CVD, while even higher temperatures exceeding 800°C are required for PVD. These conditions suggest the difficulty of growing GaN thin films because of their high melting temperature and high energy bandgap. To date, many PVD processes, including sputtering, MBE, and pulsed laser deposition, have been used to grow GaN thin films [11–13]. Among these processes, radio frequency (RF) magnetron sputtering is a representative PVD process [14–18]. Owing to its high melting temperature of 1600°C, GaN requires high energy to form a thin film. Therefore, high processing energy with high vacuum pressure are key requirements in the processing chamber system. Owing to its reliability and controllability, the substrate heating method is preferred to provide sufficient energy for the thin film process during PVD. However, high thermal energy cannot be transferred to the thin films in a vacuum chamber system with a direct substrate heating process because high vacuum conditions cannot be sustained at the high temperatures required in the processing chamber. In addition, re-evaporation occasionally occurs because of the high substrate temperature in the chamber. Therefore, high-quality thin films cannot be grown using a standard magnetron sputtering process at elevated temperatures.