Position-Dependent Conductivity Transition by Intrinsic Defects in Cd1-xZnxTe Crystal
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摘要: 在富Te生长条件下,采用垂直布里奇曼法(vertical Bridgman method, VB)生长的部分碲锌镉(Cd1-xZnxTe, CZT)晶体内存在导电类型转变界面。为深入探讨碲锌镉晶体导电类型转变界面形成的原因,结合晶体导电类型和红外光谱透过率的测试结果与第一性原理的理论计算进行分析,结果表明,碲锌镉晶体内的导电类型转变界面是晶体生长过程中形成的Cd空位(VCd)缺陷与Cd间隙(Cdi)缺陷导致的。在富Te条件的生长过程中,Cd空位缺陷易于形成,碲锌镉晶体材料中含有大量的Cd空位缺陷,材料的导电型为p型。在晶体生长结束阶段的降温过程中,Cd原子会扩散至碲锌镉晶体中,促进了Cd间隙缺陷的形成,在碲锌镉晶体材料中形成Cd间隙缺陷,导致晶体材料的导电性转变为n型。Abstract: In this study, the formation of a position-dependent conductivity transition in Cd1-xZnxTe crystals is investigated. The results indicate that the transition from p- to n-type Cd1-xZnxTe (x = 0.04) can be ascribed to the formation of the VCd-Cdi interface. Cd vacancies (VCd) are easily generated in the Te-rich condition crystal growth process and are responsible for the p-type conductivity. However, Cd vacancies are filled and the n-type defect, Cd interstitial (Cdi), form in the Cd-rich condition. This leads to the transition from p-type to n-type conductivity during the growth of Cd1-xZnxTe (x = 0.04).
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Key words:
- Cd1-xZnxTe /
- position-dependent conductivity transition /
- Cd vacancy /
- diffusion
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图 1 布里奇曼法生长的碲锌镉晶体:(左图)电类型由p型向n型转变的界面;(右图)碲锌镉晶体的Te沉积相夹杂/包裹体像图
Figure 1. Image of a Cd0.96Zn0.04Te crystal grown by vertical Bridgman method: (Left) As schematically illustrated by different colors leads to a position-dependent transition from p- to n-type conductivity; (Right) Te inclusion /precipitation in Cd1-xZnxTe
图 3 (a) 碲锌镉晶体结构;(b) 2×2×2超胞碲锌镉晶体的总电子态密度和分波电子态密度图;(c) 碲锌镉本征缺陷的单电子能态结构图;(d)~(g)分别是具有1.1 mm厚的本征碲锌镉晶体(d)、含Cd空位VCd缺陷(e)、Cd间隙Cdi(f)缺陷和Te取代CdTeCd(g)缺陷碲锌镉晶体的反射谱R、吸收谱A和透光谱T
Figure 3. Crystal structure of Cd1-xZnxTe(a), total and partial density of states of Cd28Zn4Te32 supercell containing eight times (2×2×2) the volume of the unit cell(b), calculated single particle electron energy states for the Cd28Zn4Te32 crystals neutral intrinsic defects(c), transmission(T), reflection(R), and absorption(A) spectra of a freestanding 1.1 mm-thick Cd28Zn4Te32, Cd27Zn4Te32, Cd29Zn4Te32, Cd27Zn4Te33 wafer (d)~ (g), respectively
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