在CaF_2衬底上常压MOCVD法生长ZnSe-ZnTe应变超晶格

GROWTH OF ZnSe-ZnTe STRAINED-LAYER SUPERLATTICES ON CaF_2 (111) SUBSTRATE BY ATMOSPHERIC PRESSURE METAL ORGANIC CHEMICAL VAPOR DEPOSITION

我们首次在透明衬底CaF_2上生长了ZnSe-ZnTe应变超晶格。通过X射线衍射测量,观测到多级卫星峰,表明超晶格周期结构的形成.光致发光光谱峰值的蓝移,表征ZnSe-ZnTe超晶格中应变与量子尺寸效应的存在.吸收光谱中几个明显的拐点,表明了发生在超晶格导带与价带子能级之间的多级跃迁的形成。

The growth of ZnSe-ZnTe strained-layer superlattices on CaF2(111) substrate by atmospheric pressure metal organic chemical vapor deposition is reported for the first time. The typical growth conditions are shown in Table 1. The critical thickness Of ZnTe/CaF2 heterojuncticn is appraised as 2nm. With X-ray diffraction measurement, we observe many satellites of ZnSe-ZnTe SLS around(333) reflection, which confirms the formation of the period structure of superlattices, and shown in. Fig.1.The lattice parameters of ZnTe, Zr.Se and CaF2 are 0.6101 nm, 0.56686 nm, 0.54626 nm, corresponding to the Bragg diffraction angles 29 around (333) reflection 82.00, 89.837 and 94.231 degree,respectively. We found that the satellites around the ZnSe Bragg angle are very strong, while the satellites around ZnTe Brafg argle are too weak to observe them in Fig.1. So the thickness of ZnSe layers is much larger than that of ZnTe layers.Using the zero-order peak corresponding to the average perpendicular lattice parameter and the superlattice periodicity calculation, we obtain the data of ZnSe and ZnTe layers a.s 6nm, 0.6nm, respectively.For ZnSe (6nm)-ZnTe(0.6nm) SLS/CaF2 (111), the first ZnTe layer on substrate CaF2 can not be accommodated by elastic deformation, and the lattice constant of the SLS parallel to the surface determined by Eq. 1 does not equal the lattice constant of the substrate.Fig.2 is the photoluminescence emission spectrum of ZnSe (6nm)-ZnTe(0.6nm) SLS/CaF2 with the excitation of the line 337.1nm of N2-laser at 77K. The peak value is 630nm which shows the existence of strain and quantum confinement effects. Fig.3 is the optical absorption spectrum of ZnSe(6nm)-ZnTe(0.6nm) SLS on CaF2 transparent substrate with the measurement of UV-3000 Double Wave-length/Dual Beam Recording Spectrophotometer at room temperature. The first absorption peak at 640nm is thought to be the optical absorption due to the transition Between the n=1 electronic subband in ZnSe layers and the n=1 heavy hole subband in ZnTe layers.