Development of reactively controlled super-sonic nozzle beam epitaxial growth technique

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We developed the growth technique which is called "supersonic beam epitaxy" (SSBE). Using the technique, we in-situ observed and understood dynamic processes of GaAs growing surface in a milisecond range by means of high-speed RHEED and RD.Precise control of the growth rate to 1/10 monolayr per pulse was also achieved simply by arrangeing the pulse width. Furthermore, we succeeded in the control of surface reaction processes by using supersonic beam source. As a result, by using supersonic beam source, incorporation of carbon inpurities into the crystal during the growth was greatly suppressed and the concentration of carbon in the GaAs crystal is two-order less than that using usual one. All these indicates that the technique is useful and hopeful for the future applications.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 diodes (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. Since it was reported that CH_3SiH_3 begins to decompose above 800ﾟC,it is difficult to use it because usually GSMBE growth is carried out at a relatively low temperature. 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.