钪与氧空位共掺杂锐钛矿相TiO2的形成能与电子结构的第一性原理研究

采用基于密度泛函理论的第一性原理研究了钪(Sc)、氧空位(O_V)单/共掺杂锐钛矿相TiO₂,对晶体结构、形成能以及电子结构进行了对比分析.研究结果表明，Sc-TiO₂在富氧环境下缺陷形成能为负值，富钛环境下缺陷形成能为正值，表明Sc-TiO₂只能在富氧环境下制备；O_V-TiO₂、Sc-O_V-TiO₂在富氧或富钛环境下缺陷形成能均为负值，但富氧环境下形成能更低；O_V-TiO₂的0/1-缺陷电荷转变能级为深能级，而Sc-TiO₂的0/1-缺陷电荷转变能级则属于相对较浅能级；与纯锐钛矿相TiO₂相比，Sc-TiO₂的禁带宽度略有减小，但O_V-TiO₂、Sc-O_V-TiO₂禁带宽度变宽.     

γ辐照室温短波HgCdTe光伏器件的导纳谱研究

利用变频导纳谱研究了γ辐照前后Hg_1－xCd_xTe(x=0.6)n⁺-on-p结中的深能级缺陷．辐照前其缺陷能级位置在价带上0.15 eV,俘获截面σ_p＝2.9×10^-18cm²,缺陷密度N_t＝6.5×10¹⁵cm^-3,初步认为是Hg空位或与其相关的复合缺陷;经过10⁴Gy的γ辐照后其能级变得更深,在价带上0.19 eV,同时其俘获截面增加了近一个数量级,而缺陷密度基本上没有变化．γ辐照引入的这种能级变化最终使器件的性能(探测率)下降了1/2以上． 关键词：     

半导体缺陷能级的应力效应

本文讨论用瞬态方法测量立方半导体缺陷能级应力移动和判别缺陷势对称性的有关问题。对于简并能级E_s引入应力下分裂平均值E_s,它具有原哈密顿群对称操作不变性,因此可以用群论方法得出应力系数间关系并用以判断缺陷势对称性。比如当缺陷势具有T群以上对称时,缺陷能级平均值E_T相对导带底或价带顶单轴应力系数(?(E_c-E_T))/(?F)或(?(E_T-E_v))/(?F)与应力F方向无关且等于流体静压系数的1/3。也讨论了C_3v对称缺陷势的情况。缺陷能级对导带的平均电子发射率e_n和俘获率c_n满足简洁关系 e_n=g_Tg_c^-1c_nN′_ce^{(-(E_c-E_T)/kT)}。指出通过测量e_n的应力关系判断缺陷势对称性的各种方案比较。分析了用瞬态法测量e_n有关问题。当E_T分裂但诸能级间允许跃迁时,瞬态讯号呈单指数衰减,时间常数为e_n^-1。当E_T分裂但诸能级间禁止跃迁时,瞬态讯号呈多指数衰减。用初始斜率可求得e_n。 关键词：     

La-Ce共掺杂锐钛矿TiO2的缺陷形成能和电子结构分析

采用基于密度泛函的第一性原理研究了稀土元素La、Ce共掺杂锐钛矿相TiO₂的缺陷形成能,缺陷电荷转变能级以及电子结构.研究发现,富氧状态下La、Ce掺杂以及La-Ce共掺的缺陷形成能均为负值,而贫氧状态下La、Ce掺杂形成能为正,表明La、Ce的掺杂TiO₂只能在氧气氛制备条件下进行;替代Ti掺杂缺陷电荷转变能级计算结果表明:0/1-的缺陷电荷转变能级分别位于VBM上面0.522 eV及2.440 eV处;与纯锐钛矿相TiO₂相比,La、Ce单掺杂以及La-Ce共掺杂均能减小TiO₂的禁带宽度,但共掺杂体系的禁带宽度更窄,因此共掺杂体系将更有利于提高TiO₂对可见光的响应能力和光催化性能.     

Si中S0对、Se0对和Te0对的电子结构

利用紧束缚近似下的格林函数方法,讨论了Si中(S⁰)₂,(Se⁰)₂及(Te⁰)₂基态的能级和波函数。分析了几种不同的观点。(S⁰)₂,(Se⁰)₂及(Te⁰)₂均在禁带中引入一个对称性的A_1g能级和一个反对称性的A_2u能级,二者都是填满的。现有实验观测到的是较高的A_1g能级。从理论上指出了对称性的A_1g能级反而高于反对称性的能级的原因。而Si中(Se₂)⁺的g因子测量值和(S₂)⁺,(Se₂)⁺的ESR实验结果也支持本文的观点。 关键词：     

电子辐照硅层中缺陷能级的研究

用12MeV电子辐照硅p⁺n结,在硅中除引入氧空位E₁(E_c-0.19eV),双空位E₂(E_c-0.24eV)和E₄(E_c-0.44eV)外,还引入缺陷E₃(E_c-0.37eV)。用DLTS方法和反向恢复时间测量研究了这些能级的退火行为,可以看到,E₃的退火温度最高(≈520℃)。由退火特 关键词：     

BeAl2O4:Cr3+的晶场能级

金绿宝石中镜对称格位上Cr³⁺(Ⅱ)离子的⁴T₂,⁴T₁和²E能级与该材料的激光运转有关。⁴T₂和⁴T₁能级各分裂成三个子能级。为从偏振吸收谱上确定BeAl₂O₄:Cr³⁺的能级图,本文计算了⁴T₂和⁴T₁的分裂,找到了对谱方法,得到了表征能级分裂的参量K_{1和K2的值。最后给出了以低点群不可约表示标号的、BeAl2O4:Cr³⁺(Ⅱ)的晶场能级图。 关键词：}     

高压下缺陷对锐钛矿相TiO2多晶电输运性能的影响:交流阻抗测量

采用高压原位阻抗谱测量技术对锐钛矿Ti O₂多晶的电输运性质进行了系统研究.在6.4, 11.5和24.6 GPa压力处发现了晶粒和晶界的电阻、参数因子和弛豫频率的反常变化行为.研究分析表明:6.4和11.5 GPa压力点分别对应着Ti O₂由锐钛矿转变为a-Pb O₂,再转变为斜锆石的结构相变,当压力高于24.6 GPa时,Ti O₂完全转变为斜锆石相.通过分析晶粒和晶界电阻在压力作用下的变化行为可知,本征缺陷的存在对Ti O₂高压下电输运性质的变化起着关键的作用.在6.4 GPa压力处,相变的发生导致缺陷的作用发生了变化,由作为复合中心的深能级缺陷转变为向导带和价带提供载流子的浅能级缺陷,并且作为浅能级缺陷存在至实验最高压力点38.9 GPa,浅能级缺陷在能带中的位置也随着相变发生而改变.晶粒和晶界的激活能随着压力升高而降低,表明高压下载流子在晶粒和晶界的输运变得更加容易.此外, Ti O₂晶粒和晶界的弛豫频率比值随压力的升高而不断减小,高压下的晶界效...     

深能级对AlGaInP/GaAs异质结双极晶体管性能的影响

用深能级瞬态光谱和光致发光(PL)方法研究了AlGaInP/GaAs异质结双极晶体管(HBT)发射区AlGaInP中的深能级.得到了两个深能级,分别为E_c-E_t1＝0.42eV和E_c-E_t2＝0.59eV,其复合截面为σ_n1＝6.27×10^-17cm²和σ_n2＝6.49×10^-20cm². 关键词：     

ZnS:Ho3+的辐射跃迁和无辐射过程

本工作研究了Ho³⁺离子在宽禁带半导体ZnS中的辐射跃迁和无辐射过程。用发射谱线的积分光强和激发态寿命获得ZnS:Ho³⁺的强度参数Ω_λ,同时计算了九个激发态的辐射跃迁几率和能级寿命。另外,通过在不同温度下测定Ho³⁺离子⁵G₆,³K₈,⁵F₂,⁵F₃和⁵S₂(⁵F₄)能级的发射光强和寿命的方法,研究了这几个激发态间的无辐射过程,其中⁵G₆,³K₈,⁵F₂和⁵F₃这四个能级是处于热平衡状态,而⁵F₃与⁵S₂(⁵F₄)能级间存在五个声子((1/n)ω_Lo=351cm^-1)参与的多声子弛豫过程。 关键词：     

等离子体氧轰击硅生成缺陷的研究

本文对等离子体氧轰击硅产生的缺陷进行了研究。发现等离子体氧轰击在硅中引入两个缺陷E₁(E_c—0.46eV)及E₂(E_c—0.04eV)。测量了缺陷的光电离截面谱,分析表明,缺陷E₂的电子声子相互作用很强,其Frank-Condon移动达0.76eV,缺陷E₁的电子声子相互作用较小,其Frank-Condon移动为0.04eV。由实验结果得到与缺陷E₁、E₂相耦合的声子模分别为hω_p⁽¹⁾=28meV,hω_p⁽²⁾=20meV。 关键词：     

注氮GaAs中的深能级及其对自由载流子的补偿

详细研究了注氮n型GaAs中深的和浅的杂质缺陷的电学性质。深能级瞬态谱(DLTS)技术测量表明,能量为140keV和剂量为1×10¹³cm^-2的氮离子注入并经800℃退火30min的GaAs中存在四个电子陷阱,E₁(0.111),E₂(0.234),E₃(0.415),E₄(0.669)和一个空穴陷阱H(0.545),而在能量为20keV和剂量为5×10^{14关键词：}     

Deep level transient spectroscopy (DLTS) study of defects introduced in antimony doped Ge by 2 MeV proton irradiation

Deep level transient spectroscopy (DLTS) and Laplace-DLTS have been used to investigate the defects created in Sb doped Ge after irradiation with 2 MeV protons having a fluence of 1×10¹³ protons/cm². The results show that proton irradiation resulted in primary hole traps at E_V +0.15 and E_V +0.30 eV and electron traps at E_C ?0.38, E_C ?0.32, E_C ?0.31, E_C ?0.22, E_C ?0.20, E_C ?0.17, E_C ?0.15 and E_C ?0.04 eV. Defects observed in this study are compared with those introduced in similar samples after MeV electron irradiation reported earlier. E_C ?0.31, E_C ?0.17 and E_C ?0.04, and E_V +0.15 eV were not observed previously in similar samples after high energy irradiation. Results from this study suggest that although similar defects are introduced by electron and proton irradiation, traps introduced by the latter are dose dependent.     

Study of deep level defects in doped and semi-insulating n-6H-SiC epilayers grown by sublimation method

Deep level transient spectroscopy (DLTS) is employed to study deep level defects in n-6H-SiC (silicon carbide) epilayers grown by the sublimation method. To study the deep level defects in n-6H-SiC, we used as-grown, nitrogen doped and nitrogen-boron co-doped samples represented as ELS-1, ELS-11 and ELS-131 having net (N_D–N_A) ∼2.0×10¹² cm⁻³, 2×10¹⁶ cm⁻³ and 9×10¹⁵ cm³, respectively. The DLTS measurements performed on ELS-1 and ELS-11 samples revealed three electron trap defects (A, B and C) having activation energies E_c – 0.39 eV, E_c – 0.67 eV and E_c – 0.91 eV, respectively. While DLTS spectra due to sample ELS-131 displayed only A level. This observation indicates that levels B and C in ELS-131 are compensated by boron and/or nitrogen–boron complex. A comparison with the published data revealed A, B and C to be E₁/E₂, Z₁/Z₂ and R levels, respectively.     

<Emphasis Type="Italic">I-V,C-V</Emphasis> and deep level transient spectroscopy study of 24 MeV proton-irradiated bipolar junction transistor

This paper describes the effect of 24 MeV proton irradiation on the electrical characteristics of a pnp bipolar junction transistor 2N 2905A. I-V, C-V and DLTS measurements are carried out to characterize the transistor before and after irradiation. The properties of deep level defects observed in the bulk of the transistor are investigated by analysing the DLTS data. Two minority carrier levels, E _C − 0.27 eV and E _C − 0.58 eV and one majority carrier level, E _V +0.18 eV are observed in the base collector junction of the transistor. The irradiated transistor is subjected to isochronal annealing. The influence of isochronal annealing on I-V, C-V and DLTS characteristics are monitored. Most of the deep level defects seem to anneal out above 400°C. It appears that the deep level defects generated in the bulk of the transistor lead to transistor gain degradation. A comparison of proton- and electron-induced gain degradation is made to assess the vulnerability of pnp transistor as against npn transistors.     

Photoionization cross sections of E levels in electron-irradiated n-type GaAs

The spectral shape of the photoionization cross sections of E₁-E₃ levels and the low-energy part of the photoionization cross sections of E₄, and E₅ levels are determined. It has been shown that radiation defects with which these levels are associated are characterized by a strong lattice relaxation of magnitude 0.5 eV. The red absorption edge for these levels in p-type GaAs has been found to lie at photon energies greater than E_g (except, possibly, level E₅).Translated from Izsvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5-, pp. 24–28, May, 1986.     

Electronic and annealing properties of the E0.31 defect introduced during Ar plasma etching of germanium

Low energy (±80 eV) Ar plasma etching has been successfully used to etch several semiconductors, including GaAs, GaP, and InP. We have studied the only prominent defect, E_0.31, introduced in n-type Sb-doped Ge during this process by deep level transient spectroscopy (DLTS). The E_0.31 defect has an energy level at 0.31 eV below the conduction band and an apparent capture cross-section of 1.4×10⁻¹⁴ cm². The fact that no V-Sb defects and no interstitial-related defects were observed implies that the etch process did not introduce single vacancies or single interstitials. Instead it appears that higher order vacancy or interstitial clusters are introduced due to the large amount of energy deposited per unit length along the path of the Ar ions in the Ge. The E_0.31 defect may therefore be related to one of these defects. DLTS depth profiling revealed the E_0.31 concentration had a maximum (6×10¹³ cm⁻³) close to the Ge surface and then it decreased more or less exponentially into the Ge. Finally, annealing at 250 °C reduced the E_0.31 concentration to below the DLTS detection limit.     

Inductively coupled plasma induced deep levels in epitaxial n-GaAs

The electronic properties of defects introduced by low energy inductively coupled Ar plasma etching of n-type (Si doped) GaAs were investigated by deep level transient spectroscopy (DLTS) and Laplace DLTS. Several prominent electron traps (E_c—0.046 eV, E_c—0.186 eV, E_c—0.314 eV. E_c—0.528 eV and E_c—0.605 eV) were detected. The metastable defect E_c—0.046 eV having a trap signature similar to E1 is observed for the first time. E_c—0.314 eV and E_c—0.605 eV are metastable and appear to be similar to the M3 and M4 defects present in dc H-plasma exposed GaAs.     

The defects produced by electron irradiation in tellurium-doped germanium

Abstract

The nature of the irradiation induced defects in germanium single crystal doped with tellurium was studied by DLTS and electrical measurements.

The E_c-0.21 eV level produced by irradiation with 1.5 MeV electrons was studied by DLTS technique. It was found that the defect associated with the E_c-0.21 eV level is divacancy. The E-center like defect (group V impurity-vacancy pair) introduces the E_c-0.20 eV level in samples doped with group V impurity. The level introduced by tellurium (group VI impurity)-vacancy pair is located at deeper than E_c-0.21 eV.

The E_c-0.16 eV level was generated by the annealing at 430 K. A model for the defect associated with the level is proposed to be a tellurium-vacancies complex.     

Concentrations of radiation defects with almost isoenergetical levels in silicon

Isochronous annealing of radiation defects with almost isoenergetical levels (indistinguishable from each other by means of temperature dependence of the majority charge carriers concentration) in silicon is studied. The concentrations of G- and A-centres with a level E _c?0.17 eV in n-Si and some (unidentified) vacancy-type and V₂+B complexes with a level E _v+0.22 eV in p-Si are determined.