Microscopic analysis on surface reaction induced by laser irradiation and its application to atomic layr epitaxy

在金属有机分子束外延（MOMBE）中，用激光触发同时供给三乙基镓和热裂解的PH_3，实现了GaP生长的原子层控制。在较低的衬底温度下，用N_2激光器发射的紫外光提高了GaP的生长速率。生长速率由激光脉冲之间的TEGa供应或光子数控制，并且其在高TEGa供应下显示饱和。用反射式高能电子衍射（RHEED）方法研究了350 ℃低温下脉冲激光辐照GaP生长引发的表面反应，发现激光辐照后，RHEED强度急剧下降，然后逐渐恢复。突然的减少表明，吸附在GaP表面上的TEGa被激光照射光分解。强度恢复对PH_3流量有很大的依赖性，表明强度恢复与光分解的TEGa和P原子之间的表面反应有关。这一结果表明，TEGa的激光分解和GaP的形成交替发生在源气体的连续供应。这开辟了一种新的模式，ALE触发激光照射源气体没有交替供应。

Control of GaP growth at the atomic-layr level has been achieved by laser-triggering in metalorganic molecular beam epitaxy (MOMBE) under a simultaneous supply of triethylgallium and thermally cracked PH_3. The growth rate of GaP was enhanced at low substrate temperatures by ultraviolet light emitted from a N_2 laser. The growth rate is controlled by either the TEGa supply between laser pulses or the photon number, and it shows saturation with a high TEGa supply. This suggests that the adsorption of TEGa on a surface saturates.Surface reactions triggered by pulsed laser irradiation for GaP growth were studied with reflection high-energy electron diffraction (RHEED) at a low temperature of 350ﾟC IN MOMBE.On the laser irradiation, the intensity of RHEED showed an abrupt decrease followed by gradual recovery. The abrupt decrease indicates that adsorbed TEGa on a GaP surface is photo-decomposed by the laser irradiation. The intensity recovery had much dependence on PH_3 flow rate, which indicates that the intensity recovery is related with surface reaction between photo-decomposed TEGa and P atoms. This result shows that the decomposition of TEGa by laser irradiation and the formation of GaP occur alternately under continuous supply of source geses. This opens up a new mode of ALE triggered by laser irradiation without alternate supply of source gases.