Crystal growth of III-V nitride semiconductor and its applications by short pulse supersonic beam epitaxy

宽带隙GaN和相关的III-V氮化物材料在光学器件，特别是蓝光和紫外光发光二极管(LED)和激光二极管(LD)方面显示出很大的潜力。人们已经通过MOCVD、MBE等各种生长技术来生长这类材料。我们成功地将SSBE和GSMBE两种技术结合起来，用于GaN量子点结构的制备。我们使用硅作为“抗表面活性剂”来制备GaN点，其中以甲基硅烷(CH_3SiH_3)作为硅源。据报道，CH_3SiH_3在800ﾟC以上开始分解，由于GSMBE生长通常在较低的温度下进行，无法获得硅原子，因此很难使用。但是，使用SSBE技术克服了这一困难，因为高能源束被认为促进了CH_3SiH_3分子分解成Si原子。因此，利用GSMBE在AlGaN表面成功地制备了GaN量子点结构。光致发光测试结果表明，GaN量子点在低温(10K)到室温(RT)都有一个很强的光致发光峰。此外，我们还开发了一种获得高发光强度的GaN薄膜的新技术。这被称为In-掺杂法。在该技术中，在高温生长GaN的过程中提供In助熔剂。从光致发光数据中发现，这种方法大大提高了带边发射的发光强度。最强的一次震级大约是它的37倍。霍尔测量结果表明，In掺杂GaN样品的电子迁移率高于未掺杂GaN样品。这是提高GaN光学和电学质量的一条很有前途的途径，为未来的器件应用奠定了基础。

Wide band-gap GaN and related III-V nitride materials have shown a strong potential for use in optical devices, especially blue and ultraviolet light emitting diodes (LEDs) and laser diodea (LDs). Many efforts have been done to grow such kind of materials by various growth techniques, such as MOCVD, MBE and etc. We successfully combined two techniques namely SSBE and GSMBE together, for the fabrication of GaN quantum dot structures. We used Si as an "anti-surfactant" for the GaN dot fabrication, where methylsilane (CH_3SiH_3) was used as a Si source. It was reported that CH_3SiH_3 begins to decompose above 800ﾟC, therefore, it is difficult to use it because usually GSMBE growth is carried out at a relatively low temperature and no Si atoms could be obtained. But, by using SSBE technique, this difficulty was overcome since high energy of the source beam is thought to enhance the decompositon of the CH_3SiH_3 molecules into Si atoms. As a result, GaN quantum dot structures were successfully fabricated by GSMBE on the AlGaN surfaces. Photoluminescence (PL) measurement results showed that there was a strong PL peak from GaN QDs and this peak could be observed from low temperature (l0K) to room temperature (RT).Furthermore, we developed a new technique to obtain high PL intensity of thin GaN film. This is called In-doping method. In this technique, In flux is supplied during the GaN growth at high growth temperature. From PL data, it was found that the PL intensity of band-edge emission was greatly enhanced by this method. The strongest one is about 37 times stronger in magnitude. Hall measurement results show that the electron mobility of In-doped GaN sample is higher than that of non-doped one. This is a promising way to improve the GaN quality, both optical and electrical, for the future device application.