Light up-conversion effects of ZnSeTe strained superlattices

在这项研究中，我们生长了具有[(7,2)_6(2,5)_1]_100的双子带（DSB）结构的ZnSe-ZnTe应变超晶格。通过HRXD、拉曼散射和PL光谱激发强度依赖性的测量，分析了光上转换效应的结构和机理。HRXD光谱显示（7,2）_6部分的卫星峰为0、±1和- 2阶。衍射峰与模拟计算结果一致。喇曼光谱显示了ZnSe-like LO和ZnTe-like LO声子峰，表明样品由单独的ZnTe层组成。发光光谱在1.8和2.2 eV处有两个峰。2.2 eV处的峰来自超晶格中的（7,2）_6部分。在之前的研究中，结构为[(2,2)_<12>(2,5)_3]_<30>的样品在1.9和2.2 eV处出现了PL峰。结果表明，可以通过DSB超晶格的结构控制PL峰的光子能量。在能量为1.96 eV的He-Ne激光器激发下，也出现了2.2 eV的PL峰，即1.96 eV的激光转换为能量为2.2 eV的光（上转换）。2.2 eV峰强度与激发强度呈非线性关系。这被认为是上转换的机制涉及一个阶梯过渡过程。

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.