CVD法制备硅基氮化镓薄膜

Synthesis and Characterization of the GaN Film

利用化学气相沉积法(CVD),分别以三氧化二镓(Ga2O3)和氨气(NH3)为镓源和氮源在硅衬底合成了一种由片状微晶构成的氮化镓(GaN)薄膜,实验中没有使用缓冲层。通过场发射扫描电子显微镜(FESEM)、电子能量散射谱(EDS)、X射线衍射(XRD)、高分辨电镜(HRTEM)和光致发光谱(PL)对样品进行分析,生成物为质量较好的富镓的纯氮化镓薄膜。片状氮化镓微晶表面大小约数百纳米,厚度数十纳米,薄膜表面平整、致密,没有裂纹或龟裂现象,与Si衬底结合紧密。氮化镓薄膜的带边峰位于367nm处,同时出现了黄光发射峰。并对此种氮化镓薄膜的生长机理进行了探讨。

GaN is a very important semiconductor with a wide direct bandgap （3.39 eV）, and has strong light emission in blue and UV regions. It has found extensive commercial applications in lasers and light-emitting diodes. Recently Si substrate is regarded as one of most promising substrates for GaN epitaxial growth due to its high quality, low cost, extensively existing in electronic industry and so on. However, it is very difficult to grow high quality GaN epitaxial layer due to great difference in lattice constant and thermal expansion coefficient. In our experiment, GaN film composed of crystalline microsheets was synthesized on Si（ 111 ） substrate by chemical vapor deposition, employing Ga2O3 and NH3 as Ga and N sources respectively. No buffer layer was used. The as-grown product was tested and characterized using SEM, EDS, XRD, TEM and PL. The results show that the as-grown product is a high quality GaN film which is composed of crystalline microsheets with less defects. The size of crystalline microsheets is hundreds of nanometers and the thickness in the range of tens of nanometers. GaN film integrates tightly with Si substrate, the surface of which is fiat, compact and no cracks. A strong band-edge emission peak at 367 nm（3. 378 eV） is observed. The growth mechanism is discussed briefly.