化学輸送法によるII-VIおよびI-III-VI_2族化合物半導体の結晶成長(1) : 輸送実験

The chemical transport is one of the most important methods for crystal growth of compound semiconductors . In this study, the crystal growth by the chemical transport was applied to ZnSe of II-VI and AgGaS_2 of I-III-VI_2 compound semiconductors which have been expected as the material for optoelectronic devices. The growth of ZnSe and AgGaS_2 Was made by using iodine and halides as the transport agent, where the growth parameters were source zone temperature, the temperature difference between source and growth zones, and amount of transport agent (M).
The transport rate plotted as a function of M showed the characteristic features. In case of ZnSe, the transport rate was drvided into three regrons of a gradual increase, a plateau and a steep increase with an increase of M, which resulted in fine granular, block form and needle-like crystals, respectively. In the case of AgGaS_2, the transport rate showed a maximum with an increase of M. The maximum transport rate increased in the order of Cl, Br and I in the transport agents. The crystal forms of rod and block were dependent on the transport rate.
The grown crystals were evaluated by measuring the photoluminescence (PL) spectra. All the ZnSe crystals only showed the self-activated emission peak indicating the presence of deep-level defects and nonradiative recombination centers. The spectra of the AgGaS_2 crystals were dependent upon the amount of iodine charged. With less amount of iodine, the crystals exhibited clear excitonic emissions, which means good quality of the crystal. The nonradiative recombination centers were increasingly introduced with an increase in the amount of transport agents.