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

我们开发了一种叫做“超声波束外延”（SSBE）的生长技术。利用该技术，我们用高速RHEED和RD在毫秒范围内原位观察和了解了GaAs生长表面的动力学过程，并通过简单地减小脉冲宽度，实现了生长速率精确控制在1/10单层/脉冲。此外，我们还成功地利用超声束源控制了表面反应过程。结果表明，采用超声束源可以有效地抑制晶体生长过程中碳杂质的掺入，使GaAs晶体中的碳浓度比常规源低两个数量级。宽禁带GaN及其相关的III-V族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）方面显示出了很强的应用潜力。人们已经做了很多努力来生长这种材料的各种生长技术，如MOCVD，MBE等。我们成功地结合两种技术，即SSBE和GSMBE在一起，用于GaN量子点结构的制造。我们使用Si作为GaN点制造的“抗表面活性剂”，其中甲基硅烷（CH_3SiH_3）用作Si源。由于CH_3SiH_3在800 ℃以上开始分解，因此GSMBE生长通常在较低温度下进行，难以使用。但SSBE技术克服了这一困难，因为高能量的源束被认为促进了CH_3SiH_3分子分解成Si原子。结果表明，GSMBE法成功制备出GaN量子点结构。

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.