Light up-conversion effects of ZnSeTe strained superlattices

在本研究中，我们生长了具有[（7，2）_6（2，5）_1]_100的双子带结构的ZnSe-ZnTe应变超晶格。通过高分辨X射线衍射、拉曼散射和光致发光光谱的测量，分析了样品的结构和上转换效应的机理。HRXD谱图显示了（7，2）_6部分的0、±1和-2级卫星峰。衍射峰与模拟计算结果相吻合。拉曼光谱显示出类ZnSe LO和类ZnTe LO声子峰，这意味着样品由单个ZnTe层组成。PL谱在1.8和2.2 eV处有两个峰。在2.2eV处的峰来自超晶格中的（7，2）_6部分。在以前的研究中，[（2，2）_<12>（2，5）_3]_<30>结构的样品在1.9和2.2 eV处显示出PL峰。这表明我们可以通过DSB超晶格的结构来控制PL峰的光子能量。用He-Ne激光激发也出现了2.2eV的PL峰，其能量为1.96eV，即，1.96eV的激光被转换成能量为2.2eV的光（上转换）。2.2 eV峰的强度对激发强度的依赖性指出了非线性关系。认为上转换的机理是一个阶跃转变过程。

In this investigation, we grew the ZnSe-ZnTe strained superlattices with a dual subband (DSB) structure of [(7, 2)_6(2, 5)_1]_100. The structure and the mechanism of light up-conversion effect are analyzed by the HRXD, Raman scattering and measurements of excitation intensity dependences of PL spectra. The HRXD spectra indicate the satellite peaks of 0, ±1 and - 2 order of the part of (7, 2)_6. The diffraction peaks coincide with the result of calculated simulation. The Raman spectrum shows the ZnSe-like LO and the ZnTe-like LO phonon peaks, which means the sample consists of individual ZnTe layer. The PL spectra showed two peaks at 1.8 and 2.2 eV. The peak at 2.2 eV is from the part of (7, 2)_6 in the superlattice. In the previous investigation, the sample of the structure of [(2, 2)_<12>(2, 5)_3]_<30> indicated the PL peaks at 1.9 and 2.2 eV. It is cleared that we are able to control the photon energy of PL peaks by the structure of the DSB superlattices. The PL peak at 2.2 eV appeared also by excitation with the He-Ne laser, the energy of which is 1.96 eV, I.e., the laser light of 1.96 eV is converted to the light with the energy 2.2 eV (up-conversion). The dependence of the intensity of the 2.2 eV peak on the excitation intensity pointed out a non-linear relation. It is considered the mchanism of the up-conversion involves a step process of transition.