Enhanced growth rates and reduced parasitic deposition by the substitution of Cl₂ for HCl in GaN HVPE

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• 作者：Tim Bohnen ; Hina Ashraf ; Gerbe W.G. van Dreumel ; Sjoerd Verhagen ; Jan L. Weyher ; Paul R. Hageman ; Elias Vlieg
• 关键词：A3. Hydride vapor phase epitaxy ; B1. Nitrides ; B2. Semiconducting gallium compounds
• 刊名：Journal of Crystal Growth
• 出版年：2010
• 出版时间：1 September 2010
• 年：2010
• 卷：312
• 期：18
• 页码：2542-2550
• 全文大小：1774 K

文摘

The main limitation in the application of hydride vapor phase epitaxy for the large scale production of thick free-standing GaN substrates is the so-called parasitic deposition, which limits the growth time and wafer thickness by blocking the gallium precursor inlet. By utilizing Cl₂ instead of the usual HCl gas for the production of the gallium chlorine precursor, we found a rapid increase in growth rate from 80 to 400 μm/h for an equally large flow of 25 sccm. This allowed us to grow, without any additional optimization, 1.2 mm thick high quality GaN wafers, which spontaneously lifted off from their 0.3° mis-oriented GaN on sapphire HCl-based HVPE templates. These layers exhibited clear transparencies, indicating a high purity, dislocation densities in the order of 10⁶ cm⁻², and narrow rocking curve XRD FWHMs of 54 and 166 arcsec in for the 0002 and 101−5 directions, respectively.

In view of these findings, the possibility of depositing Cl2-based HVPE GaN directly on sapphire via the standard low temperature nucleation-high temperature overgrowth process of classic HCl-based HVPE was investigated. By varying the Cl₂ flow during the 3 min long 615 °C nucleation phase, the nucleation conditions yielding smooth 0.7mm thick GaN on sapphire films were determined. The nucleation and coalescence mechanism of Cl₂-based HVPE GaN was found to proceed similar to that of HCl-based HVPE.