在ZnS_xSe_(1-x)单晶中本征缺陷的研究

STUDY OF NATIVE DEFECTS IN ZnS_xSe_(1-x) SINGLE CRYSTALS

本文用气相法生长ZnS_xSe_(1-x)(x=0.03)单晶,解理得到(110)面晶片。在组分分压(Zn或S/Se或Se)下300—800℃范围内进行热处理,在4.2K激子发射光谱中观察到与V_(Zn)(Zn空位)有关的I_1deep谱线强度的变化。当热处理温度低于300℃时,未观察到I_1deep谱线强度的变化。在300℃以上热处理样品中均观察到I_1deep谱线强度的变化。由此研究了V_(Zn)浓度随热处理条件的变化。提供了分别控制本征V_(Zn)缺陷和掺杂的实验依据。

In general, a single crystal of ZnSgSe1-x contains native defects which arise from the deviation of stoichiometry in the growth process . These defects have an effect on the electrical and optical properties of single crystals.The purpose of the present investigation is to measure the change of the concentration of Zn vacancy(VZn)in the heat-treated ZnSxSe1-x wafers using the intensity of I1deep line in the exciton emission spectra.Because I1deep line is known to arise from acceptor of VZn [4]. For this purpose a wafer specimen was fabricated by cleaving along the (110) plane of the grown ZnSx-Se1-x (x=0.03) single crystal. The wafers were heat-treated in the temperature range of 300-800℃ for 72 hrs.Under the composition (Zn or S/Se or Se) partial pressure and measured by photoluminescence at 4.2 K to observe the bound exciton emission spectra. The exciton emission spectra of the heat -treated ZnSxSe1-x in Zn pressure and in S/Se pressure at 300℃, 500℃, 800℃ have been shown in Fig,1-3 (a) and (b) , respectively. The intensity of I1deep line becomes weaker with the increasing temperature of heat- -treatment in Zn partial pressure. On the contrary, the intensity of I1deep line becomes stronger in S/Se partial pressure . This result means that the equilibrium between the vapor and the ZnSxSe1-x. solid during the heat-treatment is controlled by the Se partial pressure and the Zn partial pressure, respectively. Considering the following reaction.Se2(g) = SeSe+VZn (4)Zn(g)+VZn=ZnZn (5)where Sese and ZnZn are a Se atom and Zn atom occupying a normal Se and Zn site, respectively. Then the concentration of VZn increases with the increasing Se pressure, and decreases with the increasing Zn pressure.Dependence of the intensity ratio on the heat treatment temperature is shown in Fig. 4 . It is known from the Fig. 4 that the concentration of VZn is not changed below 300℃,but a change of concentration of VZn is observed above 300℃. Considering that VZn and Cu-doping in ZnSe can separately be controlled. Effective control of native defects and doped impurities in compound semiconductors was proposed in this report.