Preparation of nano-diamond films on GaN with a Si buffer layer
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摘要: 本文研发了一种简便有效的在GaN半导体衬底上直接生长纳米金刚石膜的方法。研究发现，直接将GaN衬底暴露于氢等离子体中5 min即发生分解，且随着温度从560℃升高至680℃，这种分解反应愈加剧烈，很难在GaN衬底上直接形成结合力良好的纳米金刚石膜。通过在GaN衬底上镀制几纳米厚的硅过渡层，在富氢金刚石生长环境下，抑制了GaN衬底的分解，同时在GaN衬底上沉积了约2 μm厚的纳米金刚石膜。硅过渡层厚度是决定纳米金刚石与GaN衬底结合力的主要因素。当硅过渡层厚度为10 nm时，纳米金刚石膜与GaN衬底呈现出大于10 N的结合力，可能与硅过渡层在金刚石生长过程中向SiC过渡层转变有关。Abstract: Gallium nitride (GaN) has been widely used in electronic and optoelectronic devices because of its unique electrical properties. However, its low thermal conductivity and the high thermal boundary resistance at the interface between GaN and substrates such as Si and Al2O3 prevent efficient heat dissipation from the heated regions, which limits the further development of GaN-based high power devices. Diamond, with the highest thermal conductivity, has been considered to be one of the most promising heat sink materials. However, it is hard to prepare a diamond film on a GaN substrate because there is a high thermal expansion coefficient difference and also a large lattice mismatch between them. An approach to prepare a nano-diamond film on a GaN substrate by incorporating a Si buffer layer has been proposed. A GaN substrate decomposes significantly from 560 to 680℃ when exposed to ahydrogen plasma for 5 min and no adhesive nano-diamond film can be directly grown on it. This decomposition is significantly suppressed by the presence of a Si buffer layer and a nano-diamond film about 2 μm thick can be deposited on a GaN substrate by microwave chemical vapor deposition using CH4 as the carbon source. With an optimum Si layer of 10 nm, the adhesive force between the nano-diamond film and the GaN substrate reaches 10N, which is ascribed to the complete conversion of the Si layer to a silicon carbidetransition layer during the deposition.
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Key words:
- GaN /
- Si buffer layer /
- Nano-diamond film /
- Direct growth /
- Decomposition
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