Optical properties of ZnSxTe1-x mixed crystals

The Raman scattering and the photoluminescence (PL) of ZnSxTe1-x mixed crystals grown by MBE, covering the entire composition range (0 less than or equal to x<1), were investigated. The results of Raman studies show that the phonons in ZnSxTe1-x mixed crystals display two-mode behavior. In addition, photoluminescence spectra obtained in backscattering and edge-emission geometries, reflection spectra and the temperature dependence of the photoluminescence of ZnSxTe1-x from 10 to 300K were employed to find out the origins of PL emissions in ZnSxTe1-x with different x values, The results indicate that the emission bands, for the samples with small x values, can be related to the band gap transitions or a shallow level emission center, while for the samples with large x values, they are designated to strong radiative recombinations of Te isoelectronic centers.

ZnS中Te等电子中心的时间分辨光谱研究

用时间分辨光谱研究了很大的Te组分范围内的ZnS1-xTex(x=0.005-0.85)合金的发光动力学特性,结果表明:不同形态的Te等电子中心具有不同的辐射复合寿命,从几个ns到几十个ns的范围内变化,当x=0.15左右时,寿命达到最大值(约40 ns).其物理机理源于不同的Te等电子中心具有不同的局域化特性.当Te组分较小时,等电子中心从Te1逐渐演变到Te2,Te3或Te4时,相应发光寿命增加,表现出不断增强的激子发光局域化特性;而当Te组分较大时,Te原子团变得较大,其局域势与基体原子势的相互作用增强,等电子中心的局域化特性减弱,而基体价带扩展态特征变得明显起来,相应发光寿命逐渐减小.还研究了激子束缚能随Te组分的变化以及发光强度随温度的变化关系,所得结果进一步支持了时间分辨光谱研究所得到的结论.