Vapor Phase Epitaxy of Copper Chalcopyrites Having Wide Band Gaps

本课题组利用CuCl源、GaCl3源、H_2S源和Ar载流子气相外延生长了CuGaS_2在GaAs和ZnS/GaAs衬底上的生长。在前人研究的基础上，本研究的目的是实现CuGaS_2的原子层外延生长(ALE)，并探索控制该化合物化学计量比的可能性。在GaP衬底上交替加入金属氯化物和H_2S气体，以提供H_2S气体量，成功地生长了ALE。这种生长是在CuCl3和GaCl3金属氯化物同时加入的情况下发生的，这表明黄铜矿结构中的金属原子是自排列的。发现了一个有趣的生长方向变化现象，表明在生长过程中发生了金属原子的重排，为H_2S气体的周期变化提供了依据。A_1模拉曼散射强度的基本恒定和低温下自由激子发射的出现分别导致了外延层的高均匀性和高质量。本研究为I-III-VI_2化合物半导体的生长提供了基本的认识，并有助于控制外延层的性能，包括化学计量比。

Successful vapor phase eptaxial growth of CuGaS_2 on GaAs and ZnS/GaAs substrates was reported by our group using CuCl, GaCl_3 and H_2S sources and Ar carrier gas. On the basis of the previous study, the purpose of this research is to attain atomic layer epitaxial growth (ALE) of CuGaS_2 and to search a possibility of controlling stoichiometry of this compound.Evidence of successful ALE growth on GaP substrates with alternate feeding of metal chrorides and H_2S gas was found for providing amount of H_2S gas. This ALE growth was found to occur under simultaneous feeding of metal chrorides of CuCl and GaCl_3, suggesting self arrangement of metal atoms for chalcopyrite structure. An intersting phenomenon of growth direction change which suggests an occurrence of rearrangement of metal atoms during growth was found for providing period change of H_2S gas. Essentially constant intensity of Raman scattering of A_1 mode over the grown layer and the appearance of free exciton emission at low temperatures incicate high uniformity and high quality of the layer, respectively.This study is considered to provide a basic understanding for ALE growth of I-III-VI_2 compound semiconductors and to lead to control of epitaxial layer properties including stoichiometry.