高阻In掺杂CdZnTe晶体缺陷能级的研究

Study on the Defect Energy Levels of High Resisitivity In-doped CdZnTe Crystals

利用低压垂直布里奇曼法制备了不同In掺杂量的CdZnTe晶体样品,采用低温光致发光谱(PL)、深能级瞬态谱(DLTS)以及霍尔测试等手段研究了In掺杂CdZnTe晶体中的主要缺陷能级及其可能存在的补偿机制.PL测试结果表明,在In掺杂样品中,In原子占据了晶体中原有的Cd空位,形成了能级位于E_c-18meV的替代浅施主缺陷[In_(Cd)^+],同时[In_(Cd)^+]还与[V_(Cd)^(2-)]形成了能级位于E_v+163meV的复合缺陷[(In_(Cd)^+-V_(Cd)^(2-))^-].DLTS分析表明,掺In样品中存在导带以下约0.74eV的深能级电子陷阱能级,这个能级很可能是Te反位[Te_(Cd)]施主缺陷造成的.由此,In掺杂CdZnTe晶体的电学性质是In掺杂施主缺陷、Te反位深能级施主缺陷与本征受主缺陷Cd空位和残余受主杂质缺陷补偿的综合结果.

Samples with different In dopant concentrations were grown by Low Pressure Vertical Bridgman Method. Low temperature photolmninescence （PL） spectra, Deep Level Transient Spectroscope （DLTS） and high resistivity Hall test were used to study major defects in high resistivity In-doped CdZnTe crystal and its possible compensating mechanism. The PL spectra showed that in the In-doped CdZnTe samples of high resistivity, In dopants occupied Cd vacancies, which would exist in undoped CdZnTe crystal, forming shallow donor defect [In^＋Cd], located at Ec-18meV, and the [In^＋Cd] interacted with [V^2-Cd] to form a complex defect [（In^＋Cd-V^2-Cd）-] at Ev＋163meV. The DLTS results showed that a deep level donor defect was found at 0.74eV below the conduction band, representing probably the energy level of antisite defect [Tecd]. The results indicated that the electrical properties of In-doped CdZnTe crystals were dominated by a comprehensive compensating consequence among In donor defects, deep level donor defect Te antisites, intrinsic aeceptor defect Cd vacancies and other impurities acceptor defects.