Zn掺杂和Sn空位对p型SnO2电子结构和光学性能的影响

用第一性原理计算了本征SnO2、Zn掺杂SnO2、带Sn 空位(VSn)的SnO2和Zn-VSn共掺杂 SnO2的电子结构和光学性能。结果表明,Zn 原子替位SnO2中的Sn原子后费米能级进入价带,价带顶的空能态由Zn 3d和O 2p态组成,Zn掺杂SnO2显示p型半导体性能。 带Sn空位的Zn掺杂SnO2的相对空穴数量较Zn掺杂SnO2的相对空穴数量有明显增加,Sn空位有助于增加Zn掺杂SnO2的p型导电性。Zn掺杂SnO2在可见光区域有明显的光吸收,带Sn空位的Zn掺杂SnO2的光吸收较Zn掺杂SnO2明显增强,吸收光谱发生蓝移。     

Tc-P共掺杂单层MoS2光电特性的第一性原理计算

采用第一性原理的赝势平面波方法,对比研究了未掺杂和掺杂过渡金属Tc、非金属P及Tc-P共掺杂的单层MoS2的电子结构和光学性质.计算结果表明:掺杂改变了费米面附近的电子结构,使得导带向低能方向偏移,并且带隙由K点转化为Γ点,形成Γ点的直接带隙半导体.掺杂P使带隙值变小,形成p型半导体;掺杂Tc使带隙变宽,形成n型半导体;Tc-P共掺杂,由于p型和n型半导体相互调制,使得单层MoS2转变为性能更优的本征半导体;掺杂使光跃迁强度减小,且向低能方向偏移.     

Be掺杂对ZnO电子结构和光学性质的影响

基于密度泛函理论（DFT）第一性原理计算了Zn1-xBexO化合物的电子结构和光学性质. 计算结果表明Zn1-xBexO带隙随掺杂浓度的增加而变大. 这种现象主要是由于价带顶O2p随掺杂量x的增加几乎保持不变,而Zn4s随掺杂量x的增加向高能端移动. 光学介电函数虚部计算结果表明：在2.0, 6.76eV位置随掺杂浓度的增加峰形逐渐消失,是由于Be替代Zn导致Zn3d电子态逐渐减少所致;而9.9eV峰形逐渐增强,是由于逐渐形成的纤锌矿结构BeO的价带O2p到导带Be2s的跃迁增加所致.     

Be掺杂对ZnO电子结构和光学性质的影响

基于密度泛函理论(DFT)第一性原理计算了Zn1-xBexO化合物的电子结构和光学性质.计算结果表明Zn1-xBexO带隙随掺杂浓度的增加而变大.这种现象主要是由于价带顶O2p随掺杂量x的增加几乎保持不变,而Zn4s随掺杂最x的增加向高能端移动.光学介电函数虚部计算结果表明:在2.0,6.76eV位置随掺杂浓度的增加蜂形逐渐消失,是由于Be替代Zn导致Zn3d电子态逐渐减少所致;而9.9eV峰彤逐渐增强,是由于逐渐形成的纤锌矿结构Beo的价带O2p到导带Be2s的跃迁增加所致.     

ZnO薄膜的掺杂和转型的研究进展

本征的 Zn O为高阻材料 ,电阻率高达 1 0 12 Ω· cm,如何对 Zn O进行掺杂 ,精确控制其电学性能 ,制备高质量的 n型和 p型材料是实现 Zn O应用的关键。目前 ,研究表明通过掺杂 ,n型 Zn O的制备已经能够精确控制 ,但由于 Zn O中存在的缺陷 ,如氧空位和锌间隙原子 ,Zn O天然呈 n型 ,p型的制备还有一定难度 ,本文报道了这方面研究的最新进展     

Zn掺杂β-Ga2O3薄膜的结构和光学性质

用射频磁控溅射制备了本征β-Ga2O3薄膜及Zn掺杂β-Ga2O3薄膜,研究了Zn掺杂和热退火对薄膜结构和光学性质的影响。与本征β-Ga2O3薄膜相比, Zn掺杂β-Ga2O3薄膜的微结构、光学透过、光学吸收、光学带隙以及光致发光等都发生了显著的变化。退火后的β-Ga2O3薄膜为多晶结构,Zn掺杂以后β-Ga2O3薄膜的光学带隙变窄,薄膜的结晶性变差,薄膜的光学透过降低,薄膜的紫外、蓝光及绿光发射加强。     

基于A位空位的CH_3NH_3PbBr_3带隙调控研究

利用CASTEP软件包构建出钙钛矿太阳能电池光电转化材料(CH_3NH_3)_(1-x)PbBr_3的位形结构,研究A位空位对其结构、带隙以及光学性能的影响。研究表明:带隙对空位敏感。A位空位能够使钙钛矿材料CH_3NH_3PbBr_3的带隙降低,主要的原因是由于空位导致的p型掺杂,以及周围形成的负电中心。带隙对空位含量不敏感。空位含量的多少主要影响几何结构,但对能带结构和态密度的分布影响不大,即A位空位的出现使费米能级附近的导带数量增加,该贡献主要来源于s、p壳层电子。A位空位对带隙的成功调控,使得可见光范围内实现绿光到红光光电转换成为可能。     

p型掺杂GaAs液相外延材料的光致发光研究

对Si掺杂和Zn掺杂p型GaAs液相外延材料进行光致发光研究。用发射波长为510.6nm和578.2nm的溴化亚铜激光器为激发光源,样品的低温由氦循环致冷机提供,样品室温度在10～300K中可调。在所选取的狭缝宽度下谱仪的分辨率大致为2nm,所提供的数据全部经过系统灵敏度校正并进行分峰拟合。对Si掺杂p型GaAs样品PL谱中一些主要特征进行讨论,认为A_1,A_2,A_3三个发射带分别对应着导带“尾”态中电子向价带和两个浅受主能级的跃迁,它们随温度变化的情况,和带隙宽度及电子填充状态随温度变化有关。此外,我们还观察了掺Zn的p型GaAs样品的PL谱,与掺Si样品比较,具有明显不同的特征,谱线在长波端(～950nm)的上扬趋势表明在低能区域可能存在一个与深能级复合有关的宽发射带。     

N掺杂MgZnO薄膜的p型导电稳定性研究

利用磁控溅射技术,以Mg0.06Zn0.94O为陶瓷靶材,制备了N掺杂p型Mg0.1 3Zn0.8 7O薄膜,薄膜的电阻率为42.45Ω·cm,载流子浓度为3.70×1017/cm3,迁移率为0.40cm2·V-1·s-1。研究了该薄膜p型导电性质在室温空气下随时间的变化情况。实验结果表明,薄膜的电阻率逐渐升高,载流子浓度降低,五个月以后,薄膜转变为n型导电,电阻率为85.58Ω·cm,载流子浓度为4.53×1016/cm3,迁移率为1.61cm2·V-1·s-1。真空热退火后重新转变为p型。结果显示,其p型导电类型的转变与在空气中吸附H2O或H2等形成浅施主有关。     

ZnSe发光二极管

分别用 Li 和 Cl 作为 p 型和 n 型掺杂剂,成功地制作了 ZnSep—n 结发光二极管。ZnSe 作为直接带隙Ⅱ—Ⅵ族半导体,近年来已经引起人们明显的关注。～2.7eV的室温宽带隙使其成为制作蓝色发光器件,例如 LED 和激光器的很具吸引力的材料。制作 ZnSe LED 和激光器,需要通过控制替位掺杂形成 p—n 结(或异质结)。虽然 p 型掺杂是目前制作这样器件的主要障碍,但在高浓度条件下,n 型掺杂剂的有效激活具有同等的重要性,尤其是如果要研制蓝色的ZnSe 激光器,更是如此。     

First-principles calculation of the electronic band of ZnO doped with C

Using the first-principles approach based upon the density functional theory (DFT), we have studied the electronic structure of wurtzite ZnO systems doped with C at different sites. When Zn is substituted by C, the system turns from a direct band gap semiconductor into an indirect band gap semiconductor, and donor levels are formed. When O is substituted by C, acceptor levels are formed near the top of the valence band, and thus a p-type transformation of the system is achieved. When the two kinds of substitution coexist, the acceptor levels are compensated for all cases, which is unfavorable for the p-type transformation of the system.     

First-principles study of p-type ZnO by S-Na co-doping

Using the first-principles method based on the density functional theory, the formation energy, electronic structures of S-Na co-doping in ZnO were calculated. The calculated results show that Na_Zn-S_O have smaller formation energy than Na_in-S_O in energy ranges from -3.10 to 0 eV of μ_O, indicating that it opens up a new opportunity for growth the p-type ZnO. The band structure shows that the Na_Zn system is a p-type direct-band-gap semiconductor material and the calculated band gap (0.84 eV) is larger than pure ZnO (0.74 eV). The Na_Zn-S_O system is also a p-type semiconductor material with a direct band gap (0.80 eV). The influence of S-Na co-doping in ZnO on p-type conductivity is also discussed. The effective masses of Na_Zn-S_O are larger than effective masses of Na_Zn and the Na_Zn-S_O have more hole carriers than Na_Zn, meaning the hole in the Na_Zn-S_O system may have a better carrier transfer character. So we inferred that Na_Zn-S_O should be a candidate of p-type conduction.     

氧化锌p型共掺杂精细结构的第一性原理研究

计算了ZnO材料p型掺杂精细结构,分析了p型掺杂ZnO晶体的电子结构、电荷布局、电子态密度、差分电荷。所有计算都是基于密度泛函理论(DFT)框架下的第一原理平面波超软赝势方法。计算结果表明:掺杂Ⅴ族元素(N、P、As、In)的氧化锌材料在能隙中引入了深受主能级,载流子(空穴)局域于价带顶附近。而利用加入激活施主的共掺杂技术的计算结果却表明,受主能级向低能方向移动,形成了浅受主能级。同时,受主能级带变宽,非局域化特征明显。     

Specific features of the metal-insulator conductivity transition in narrow-gap semiconductors of the MgAgAs structure type

The role of the impurity acceptor band in the conductivity of the doped and compensated ZrNiSn semiconductor is assessed. A reconstruction model of the impurity band as a result of doping the semiconductor with acceptor impurities is suggested. The electronic structure of the Zr_1?x Sc_xNiSn alloy is calculated. Oscillations of the magnetic susceptibility in the region of the metal-insulator transition (related to the Anderson transition) as the Zr_1?x Sc_xNiSn composition is varied are observed for the first time. These oscillations are believed to be a manifestation of the Coulomb gap in the impurity band as the levels of doping and compensation of the semiconductor are varied.     

N掺杂和氧空位对PbTiO3电子结构和导电性的影响研究

用第一性原理计算了P型N掺杂PbTiO3的电子密度差分、能带结构和态密度,讨论了氧空位对N掺杂PbTiO3性能的影响。在PbTiO3中掺杂N杂质后,PbTiO3的价带向高能级发生移动,费米能级进入价带顶部,带隙变窄,N掺杂PbTiO3表现出典型的P型半导体性能。当N掺杂PbTiO3中含有氧空位时,导带发生下移,受主被完全补偿。计算结果与实验数据相吻合。     

p型SiC欧姆接触理论及研究进展

碳化硅(SiC)具有宽禁带、高临界击穿电场、高热导率等优异特性,是制备高温、高频、大功率器件最理想的半导体材料之一。然而,制备良好的SiC欧姆接触尤其是p型SiC欧姆接触仍然是SiC器件研制中亟需攻克的关键技术难题。首先对p型SiC欧姆接触的形成机制及金属/SiC接触势垒理论进行了深入分析。然后,对近年来p型SiC欧姆接触的重要研究进展进行了综述,包括形成欧姆接触的金属体系,制备工艺条件,获得的比接触电阻率等,并重点讨论了p型SiC欧姆接触的形成机理。最后,对未来p型SiC欧姆接触的研究方向进行了展望。     

p型ZnO薄膜制备的研究进展

ZnO是一种性能优异的"低温蓝光工程"宽带隙Ⅱ-Ⅵ族半导体材料,但因本征施主缺陷和施主杂质引起的自补偿效应等使ZnO很难有效地实现n型向p型导电的转变。为此,阐述了ZnO薄膜的p型掺杂机理,介绍了国内外研究者在抑制自补偿、提高受主掺杂元素固溶度及寻求合适的受主掺杂元素等方面p型ZnO薄膜的最新研究进展。研究表明:增加ZnO材料中N原子固溶度的各种办法如施主-受主共掺杂、超声雾化气相淀积及本征ZnO薄膜在NH3气氛下后退火等和选择IB族中的Ag为受主掺杂元素是实现ZnO薄膜p型导电的有效措施。期望通过本综述能为国内ZnO基器件应用的p型ZnO薄膜的制备提供新思路。     

A Quasi-Classical Model of the Hubbard Gap in Lightly Compensated Semiconductors

A quasi-classical method for calculating the narrowing of the Hubbard gap between the A⁰ and A⁺ acceptor bands in a hole semiconductor or the D⁰ and D^– donor bands in an electron semiconductor is suggested. This narrowing gives rise to the phenomenon of a semiconductor transition from the insulator to metal state with an increase in doping level. The major (doping) impurity can be in one of three charge states (–1, 0, or +1), while the compensating impurity can be in states (+1) or (–1). The impurity distribution over the crystal is assumed to be random and the width of Hubbard bands (levels), to be much smaller than the gap between them. It is shown that narrowing of the Hubbard gap is due to the formation of electrically neutral acceptor (donor) states of the quasicontinuous band of allowed energies for holes (electrons) from excited states. This quasicontinuous band merges with the top of the valence band (v band) for acceptors or with the bottom of the conduction band (c band) for donors. In other words, the top of the v band for a p-type semiconductor or the bottom of the c band for an n-type semiconductor is shifted into the band gap. The value of this shift is determined by the maximum radius of the Bohr orbit of the excited state of an electrically neutral major impurity atom, which is no larger than half the average distance between nearest impurity atoms. As a result of the increasing dopant concentration, the both Hubbard energy levels become shallower and the gap between them narrows. Analytical formulas are derived to describe the thermally activated hopping transition of holes (electrons) between Hubbard bands. The calculated gap narrowing with increasing doping level, which manifests itself in a reduction in the activation energy ε₂ is consistent with available experimental data for lightly compensated p-Si crystals doped with boron and n-Ge crystals doped with antimony.     

On the specific features of the density of states of epitaxial graphene formed on metal and semiconductor substrates

Analytical expressions for the local densities of states of epitaxial graphene formed on metal and semiconductor substrates are derived on unified grounds. The conditions of strong and weak graphene-substrate coupling are considered. It is shown that, in the case of strong coupling (the interaction of carbon atoms of graphene with the substrate is much stronger than that of carbon atoms with each other), the local density of states of graphene is close to the density of states of an individual carbon adatom on both metal and semiconductor substrates. In the opposite case of weak graphene-(semiconductor substrate) coupling (the interaction of carbon atoms of graphene with the substrate is much weaker than that of carbon atoms with each other), there is no gap in the local density of states of graphene, and the Dirac point is in the band gap of the semiconductor substrate and coincides in energy with the local level of the separated (individual) carbon adatom. Graphene formed on a metal substrate also exhibits a zero-gap density of states. The problem of the band gap induced in graphene by a semiconductor substrate is considered in the general case. It is shown that, depending on the relation between the parameters of the problem, either one or two band gaps overlapping in energy with the band gap of the substrate can exist in the spectrum of graphene. The dependence of the band gaps on the strength of the graphene-substrate interaction is constructed. Numerical estimations are performed for epitaxial graphene formed on 6H-SiC {0001} faces.     

Electrical surface properties of semi-insulating and ion implanted GaAs revealed by thermo-optical acousto-electric voltage method

A thermo-optical acousto-electric voltage method is used for the determination of electrical surface properties of GaAs materials. Measurements conducted on semi-insulating substrates, some with an implanted layer, allow determination of surface conduction type, impurity activation, and photoconductivity behavior. The spectroscopic nature of the technique allows detection and characterization of energy levels in the semiconductor band gap. For the samples tested a 0.87 eV level attributed to chromium and a broad distribution of acceptor type surface states about 1.0–1.05 eV from valence band are reported. The main advantages of this measurement method are its effectiveness for the study of semiconductors over a wide range of resistivities and its nondestructive character.