Atomic Configuration of Dopant Atoms in ZnSe and ZnTe Determind by EXAFS

采用扩展x射线吸收精细结构（EXAFS）光谱和x射线吸收近边结构（XANES）光谱研究了ZnSe和ZnTe中Cl或P的原子构型和电荷态。通过测量Cl K-edge EXAFS，发现ZnSe中的Cl原子被纳入到四个配位的Se晶格位中，而ZnTe中的Cl原子从Te晶格位中移位，并且可能从一个配位向[111]方向移动。另一方面，P - k边的XANES谱表明ZnSe中存在两种电荷态。Cl掺杂ZnTe和P掺杂ZnSe的载流子补偿机制似乎不同。几乎所有II-VI类化合物都是单极材料。虽然单极的原因还不清楚，但已经提出了一些模型，如1)通过产生点缺陷进行自我补偿，2)杂质的溶解度限制，3)通过掺杂原子的位移形成DX中心。进一步研究掺杂原子周围的原子结构对理解单极现象的成因具有重要意义。采用分子束外延的方法在GaAs（100）衬底上生长了掺杂Cl的ZnSe和ZnTe。两种材料Cl掺杂剂的原子构型均约为1x10E19 cm-3。将离子注入生长在GaAs衬底上的未掺杂ZnSe和未掺杂ZnTe中制备了P掺杂材料。对ZnSe和ZnTe的P离子剂量为4x10E14 cm-2, 350 keV。采用荧光产率法在100K下测定EXAFS和XANES。在Cl掺杂的ZnTe中，Cl和Zn之间的原子距离分别为0.24 nm和0.32nm。ZnTe中Zn和Te的原子距离为0.265nm，因此可以说ZnTe中的Cl原子没有掺入取代的Te晶格位。较短键长（0.24nm）与较长键长（0.32nm）对应的Cl配位数仅为1:3。因此，Cl原子可能向[111]方向移位，形成单配位。P掺杂ZnSe的XANES光谱显示出两条吸收边，表明两种电荷态。正离子P可引起ZnSe中的载流子补偿。少

Atomic configuration and charge states of Cl or P in ZnSe and ZnTe were investigated by extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray absorption near-edge structure (XANES) spectroscopy. By measuring Cl K-edge EXAFS,it was found that the Cl atoms in ZnSe are incorporated into four coordinated Se lattice sites, however in ZnTe, the Cl atoms are displaced from Te lattice sites, and probably moved toward [111] direction and from one-coordination. On the other hand, XANES spectra of P K-edge indicates the existence of two kinds of charge states in ZnSe. The carrir compensation mechanism seems to be different between Cl doped ZnTe and P doped ZnSe.Almost all II-VI compounds are unipolar materials. Though the cause of the unipolarity is not well understood yet, some models have been suggested such as 1) self-compensation by creating point defects, 2) solubility limit of impurities and 3) formation of DX centers by a displcement of dopant atoms. It is important to cl … More arify the atomic structure around dopant atoms to understand the cause of the unipolarity.The Cl doped ZnSe and ZnTe were grown on GaAs (100) substrate by molecular beam epitaxy. The atomic configuration of Cl dopant is about 1x10E19 cm-3 for both materials. The P doped materials were prepared by ion implantation into undoped ZnSe and undoped ZnTe grown on GaAs substrates by MBE.The dose of P ions were 4x10E14 cm-2 with 350 keV for both ZnSe and ZnTe. The EXAFS and XANES measurements were performed by fluorescence yield method at 100K.In the Cl doped ZnTe, two kinds of atomic distances, 0.24 and 0.32nm, between Cl and Zn were observed. The atomic distance between Zn and Te in ZnTe is 0.265nm, so it can be said that the Cl atom in ZnTe is not incorporated into the substiutional Te lattice site. The coordination number of Cl corresponding to shorter bond length (0.24nm) to that of longer one (0.32nm) is just 1 : 3. Therefore, Cl atoms may be displaced toward [111] direction and formed one-coordination.The XANES spectra of P doped ZnSe shows two absortion edges, indicating two kinds of charge states. The positive P ion may cause the carrier compensation in ZnSe. Less