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

用扩展X射线吸收精细结构谱(EXAFS)和X射线吸收近边结构谱(XANES)研究了锌硒和碲锌中氯和磷的原子构型和电荷状态。通过对ClK边EXAFS的测量，发现ZnSe中的Cl原子被结合到四个配位的Se晶格中，而在ZnTe中，Cl原子从Te晶格中移位，并可能向[111]方向移动，从一配位移开。另一方面，P-K边的XANES谱表明，ZnSe中存在两种电荷态。掺氯和掺磷的锌硒的载流子补偿机制似乎不同，几乎所有的II-VI化合物都是单极材料。虽然单极性的原因还不是很清楚，但已经提出了一些模型，如：1)通过产生点缺陷进行自补偿，2)杂质的溶解度极限，3)通过掺杂原子的分散形成DX中心。Cl…是很重要的进一步改变掺杂原子周围的原子结构以了解产生单极化的原因。用分子束外延方法在GaAs100衬底上生长了掺氯的ZnSe和ZnTe。两种材料的氯掺杂原子构型均为1×10~(-9)E~(19)cm~(-3)。采用分子束外延技术，在未掺杂和未掺杂的砷化镓衬底上，用离子注入法制备了掺磷材料，注入剂量为4x10E14 cm-2，注入电压为350keV。在100K用荧光产生法进行了EXAFS和XANES测量。在掺氯的ZnTe中，观察到了氯和锌之间的两种原子间距，分别为0.24和0.32 nm。ZnTe中的Zn和Te之间的原子间距为0.265 nm，因此可以说，ZnTe中的Cl原子没有进入替代的Te晶格位置。较短键长(0.24 nm)和较长键长(0.32 nm)对应的氯的配位数仅为1：3，因此，氯原子可能向[111]方向移动而形成一配位。掺磷的锌硒的XANES谱显示两个吸收边，代表两种电荷状态。正的P离子可能会引起锌硒中的载流子补偿。较少

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