| Research Abstract |
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.
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