Experimental Study of the Effect of Precursor Composition on the Microstructure of Gallium Nitride Thin Films Grown by the MOCVD Process
- 8 September 2021
- journal article
- research article
- Published by ASME International in Journal of Heat Transfer
- Vol. 143 (10)
- https://doi.org/10.1115/1.4051672
Abstract
Chemical vapor deposition (CVD) is a widely used manufacturing process for obtaining thin films of materials like silicon, silicon carbide, graphene, and gallium nitride that are employed in the fabrication of electronic and optical devices. Gallium nitride (GaN) thin films are attractive materials for manufacturing optoelectronic device applications due to their wide band gap and superb optoelectronic performance. The reliability and durability of the devices depend on the quality of the thin films. The metal-organic chemical vapor deposition (MOCVD) process, which uses compounds that contain metals and organic ligands as precursors in a CVD reactor, is a common technique used to fabricate high-quality GaN thin films. The deposition rate and uniformity of thin films are critical to a successful and useful process. These are determined by the thermal transport processes and chemical reactions occurring in the reactor, and are manipulated by controlling the operating conditions and the reactor geometrical configuration. In this study, the epitaxial growth of GaN thin films on sapphire (Al2O3) substrates is carried out in two commercial MOCVD systems: a vertical rotating disk MOCVD reactor and a close-coupled showerhead MOCVD reactor. The surface morphology and crystal quality of GaN thin films have been examined using atomic force microscopy (AFM) and scanning electron microscope (SEM). This paper focuses on the composition of the precursor and the carrier gases since earlier studies have shown the importance of precursor composition. The results show that the flow rate of trimethylgallium (TMG), which is the main ingredient in the process, has a significant effect on the deposition rate and uniformity of the films. Also, the carrier gas plays an important role in deposition rate and uniformity. Using hydrogen as a carrier gas enhances the quality of the thin film but a lower deposition rate occurs on the wafer surface. On the other hand, a high flow rate of pure nitrogen gas improves the growth rate of the film. However, it decreases the uniformity of the film and promotes carbon contamination on the wafer surface. Thus, the use of an appropriate mixture of hydrogen and nitrogen as the carrier gas can improve the deposition rate and quality of GaN thin films.Keywords
This publication has 25 references indexed in Scilit:
- The influence of the working pressure on the synthesis of GaN nanowires by using MOCVDJournal of Crystal Growth, 2010
- Simulation and optimization of silicon thermal CVD through CFD integrating Taguchi methodChemical Engineering Journal, 2008
- On the flow stability in vertical rotating disc MOCVD reactors under a wide range of process parametersJournal of Crystal Growth, 2006
- Blue laser diode (LD) and light emitting diode (LED) applicationsphysica status solidi (a), 2004
- Epitaxy growth kinetics of GaN filmsJournal of Crystal Growth, 2003
- Influence of carrier gas on the morphology and structure of GaN layers grown on sapphire substrate by six-wafer metal organic chemical vapor deposition systemJournal of Crystal Growth, 2001
- Influence of the VIII molar ratio on the structural and electronic properties of MOVPE grown GaNSolid-State Electronics, 1997
- Superbright Green InGaN Single-Quantum-Well-Structure Light-Emitting DiodesJapanese Journal of Applied Physics, 1995
- High-Brightness InGaN Blue, Green and Yellow Light-Emitting Diodes with Quantum Well StructuresJapanese Journal of Applied Physics, 1995
- Thin film diamond by chemical vapour deposition methodsChemical Society Reviews, 1994