GaAs,GaP和GaAs_xP_(1-x)合金能带的计算

使用分区变分法计算了GaAs,GaP和GaAs_xP_(1-x)合金的能带。鉴于原胞内包含不同的原子,依据实际原子的大小,对不同原子球选用了不同的半径。晶体势用相应原子势的迭加势来计算。考虑到组成晶体时原子势场由于电子成键而产生畸变,因而在球外成键区选用了一些调整参数来调整势场,然后再用解析表式来逼近这种调整原子势。适当地选择调整参数使算得的能带同已知的实验值接近。对GaAs和GaP已算得了同实验结果符合的能带结构。使用所得的调整原子势进一步计算了GaAs_xP_(1-x)合金的能带。     

GexSi1-x合金中的键长及其对电子能带结构的影响

采用经验紧束缚理论，以类似闪锌矿结构的晶体模型模拟Ge_xSi_1-x合金，根据总能最小原则计算了Ge_xSi_1-x合金中的键长及点阵常数．同时以紧束缚方法计算了原子位置发生弛豫前后的电子能带结构，并与虚晶近似下的计算结果进行了比较．计算结果表明，Ge_xSi_1-x合金中的键长基本上与合金组分无关，各自接近于Ｇｅ，Ｓｉ晶体中的键长，与广延ｘ射线吸收精细结构（ＥＸＡＦＳ）测量结果符合得 关键词：     

用局域密度泛函线性丸盒轨道原子球近似超元胞法计算(Ba1-xKx)BiO3的Hopfield常数与Tc随组分x的变化

用局域密度泛函线性丸盒轨道原子球近似(LDF-LMTO-ASA)超元胞法计算(Ba_1-xK_x)BiO₃特定组分x的电子结构,其中x=0.0,0.5,1.0三种组分由扩大1倍的元胞计算;x=0.25和0.75两种组分由扩大4倍的元胞计算,所得能带参数总态密度TDOS(E_F)、分波态密度PDOS(E_F)以及自洽晶体势V^t(r),结合由实验测定的Θ_D≈210K,按McMillan强耦合公式以及Gaspari-Gyorffy近似,分别计算各原子的Hopfield常数η_t,电声子耦合常数λ以及超导转变温度T_c随组分x的变化。计算结果λ≈1而T_c最大约10K,且随x变化缓慢。与实验结果对比似乎暗示,在(Ba_1-xK_x)BiO₃中除电声子机制外,随组分变化的复杂结构相变亦将起重要的作用。 关键词：     

经验调整分区变分能带计算方法和合金能带的计算

本文提出了一种经验调整分区变分能带计算方法。它通过球外势的调整来使算得的能带更接近于实验结果。应用这一方法计算了锗和硅的能带。所得结果和实验值吻合得很好。针对在不同势场区域内用不同方法计算的特点,我们又提出了计算合金固溶体能带的新模型。运用同样的调整参数来计算锗硅合金的能带,获得了比OPW法更好的结果,从而说明这是一种有效的能带计算方法,可望在其它领域中获得更多的应用。 关键词：     

用赝势微扰法计算某些半导体的能带结构(用于GaAs,GaP和Ga[As1-xPx]合金)

用赝势微扰法计算了GaAs,GaP和Ga[As_1-xP_x]合金的能带。赝势选择的原则是使计算所得直接能隙和间接能隙与实验值相符合。计算结果表明,不但能带次序准确,而且与室温下的实验值符合得很好。基于由GaAs到GaP晶格常数和赝势是线性变化的假设,计算了GaP含量为20％,50％和80％时Ga[As_1-xP_x]合金的能带。当GaP含量为41％时,直接能隙和间接能隙相等,这一数值刚好是Spitzer和Fenner的实验值的平均值。此时,由于很好满足光激射器p-n结所要求的条件,因此可望在光激射器中得到应用,它们的能带也就有一定的参考价值。     

用积分球和分布光强计测量红、黄、绿发光二极管(LED)的总光通

为适应半导体LED发展的需要,我们设计出积分球与转动式分布光强计,可对GaAs_xP_1-x,GaP,GaAs加荧光粉三种材料制成的红、绿、黄LED的总光通和光强空间分布进行测试。由此不难算出平面封帽数码管的发光率(亮度)。为了便于和国外发表的结果作对比,用国产标准灯作定标标准后,还把标准灯和国外照度计的测试结果作了比较。结果表明,在误差范围内彼此很好地符合。 关键词：     

用赝势微扰法计算某些半导体的能带结构(用于GaAs,GaP和Ga[As_(1-x)P_x]合金)

用赝势微扰法计算了GaAs,GaP和Ga[As_(1-x)P_x]合金的能带。赝势选择的原则是使计算所得直接能隙和间接能隙与实验值相符合。计算结果表明,不但能带次序准确,而且与室温下的实验值符合得很好。基于由GaAs到GaP晶格常数和赝势是线性变化的假设,计算了GaP含量为20％,50％和80％时Ga[As_(1-x)P_x]合金的能带。当GaP含量为41％时,直接能隙和间接能隙相等,这一数值刚好是Spitzer和Fenner的实验值的平均值。此时,由于很好满足光激射器p-n结所要求的条件,因此可望在光激射器中得到应用,它们的能带也就有一定的参考价值。     

尺寸效应对非晶态TM100-xMx合金结构的影响

本文通过对非晶态合金结构的计算机模拟,研究非晶态TM_100-xM_x合金在成分基本相同条件下,M原子与TM原子尺寸比的变化对合金结构的影响。为此,分别模拟了Fe₈₀P₂₀,Co₈₁P₁₉和Fe₈₀B₂₀等非晶态合金的结构,并从径向分布函数、拓扑短程序、结构的稳定性和电子迁移引起的原子尺寸变化等方面讨论了原子尺寸的变化对非晶态合金结构的 关键词：     

(GaAs)1(AlAs)1(001)超晶格与闪锌矿结构Ga0.5Al0.5As合金虚晶能带的对应性

基于线性丸盒轨道原子球近似(LMTO-ASA)数值计算,比较(GaAs)₁(AlAs)₁(001)超晶格与闪锌矿结构Ga_0.5Al_0.5As合金虚晶能带本征态,发现它们可以用Ⅲ价和Ⅴ价原子平面的分波态进行统一描述,用这种方法详细分析超晶格与闪锌矿结构合金在布里渊区Γ,M(X)和R(L)诸点主要能带本征态之间的对应关系,讨论了超晶格布里渊区能带折叠对本征态的影响。 关键词：     

MBE GaAs1-xSbx/GaAs应变层量子阱的光调制反射光谱

本文采用光调制反射光谱技术研究了MBE GaAs_1-xSb_x/GaAs应变层量子阱。通过实验分析和理论上对受应力作用后能带结构的估算,确认在这一系统中流体静压力作用引起的能带结构变化主要出现在导带上,同时也证实了GaAs_1-xSb_x/GaAs应变层量子阱属于第Ⅱ型量子阱结构。实验结果与理论估算符合很好。 关键词：     

GaP和GaAs1-xPx中N束缚激子压力行为的理论计算

本文在Koster-Slater单带位势近似下对GaP和GaAs_1-xP_x中N等电子中心束缚激子的压力行为与能带结构的关系进行讨论与分析,得到杂质态压力系数的一个近似的解析表达式,并对N和NN_i中心能级的压力关系进行计算。同时,给出NN_i中心配位的一组新的指认。 关键词：     

Optoelectronic properties of GaAs1−xPx alloys under the influence of temperature and pressure

This work is concerned with the dependence of the electronic energy band structures for GaAs_1−xP_x alloys on temperature and pressure that is based on local empirical pseudo-potential method. The band structures of GaAs_1−xP_x alloys were calculated in the virtual crystal approximation using the EPM which incorporates compositional disorder as an effective potential.     

Hot electron energy and momentum relaxation in GaAs/AlAs and GaAs/Ga1-xAlxAs multiple quantum wells

Experimental results on high electric field longitudinal transport in GaAs/AlAs and GaAs/Ga_1-xAl_xAs multiple quantum wells (MQW) are presented and compared with the prediction of a dielectric continuum model. We draw from our experiments the following four conclusions.(i) In GaAs/Ga_1-xAl_xAs systems the dominant energy and momentum relaxation mechanism is through scattering with GaAs -modes.(ii) However, in GaAs/AlAs systems the AlAs interface mode is dominant in relaxing the energy and momentum of the quantum well electrons.(iii) The hot electron momentum relaxation as obtained from the high-field drift velocity experiments is strongly affected by the production of hot phonons as expected from a model involving a non-drifting hot phonon distribution.(iv) The importance of the AlAs interface mode in GaAs/Ga_1-xAl_xAs MQW is not the result of the intrinsic scattering rate but related to its shorter lifetime, compared to GaAs modes.     

Photoluminescence and transmission spectra of nanocrystalline GaAs（1-x）Sbx embedded in silica films

The composite films of the nanocrystMline GaAs（1-x）Sbx-SiO2 have been successfully deposited on glass and GaSb substrates by radio frequency magnetron co-sputtering. The 10K photoluminescence （PL） properties of the nanocrystalline GaAs（1-x）Sbx indicated that the PL peaks of the GaAs（1-x）Sbx nanocrystals follow the quantum confinement model very closely. Optical transmittance spectra showed that there is a large blue shift of optical absorption edge in nanocrystMline GaAs（1-x）Sbx-SiO2 composite films, as compared with that of the corresponding bulk semiconductor, which is due to the quantum confinement effect.     

Electronic Raman scattering from inter-valence band transition in photo-excited GaP and GaAs1−xPx crystals

Raman scattering from photo-created free carriers in undoped GaP and GaAs_1?xP_x (x = 0.85, 0.73 and 0.66) under high excitation intensity has been studied. Two new Raman bands have been observed and assigned to electronic transitions from the split-off hole band to the heavy hole band and from the light hole band to the heavy hole band. The spin-orbit splitting energies in these crystals have been determined from the analysis of observed Raman bands, and compared with other experimental values.     

AlxGa1-xP固溶体XPS和AES研究

采用XPS和AES对AI_xGa_1-xP(0≤x≤0.64)进行了研究。实验结果表明,组分比x增加时磷的2p结合能减小,价带顶退缩。同时鉴别和澄清了GaP微弱俄歇峰。 关键词：     

Structural and vibrational properties of dilute GaNxAs1−x(P1−x)

We report a comprehensive analyzes of the Fourier transform infrared (FTIR) absorption and Raman scattering data on the structural and vibrational properties of dilute ternary GaAs_1−xN_x,[GaP_1−xN_x] (x<0.03) alloys grown on GaAs [GaP] by metal organic chemical vapor deposition (MOCVD) and solid source molecular beam epitaxy (MBE). By using realistic total energy and lattice dynamical calculations, the origin of experimentally observed N-induced vibrational features are characterized. Useful information is obtained about the structural stability, vibrational frequencies, lattice relaxations and compositional disorder in GaNAs (GaNP) alloys. At lower composition (x<0.015) most of the N atoms occupy the As [P] sublattice {N_As[N_P]}—they prefer moving out of their substitutional sites to more energetically favorable locations at higher x. Our results for the N-isotopic shifts of local mode frequencies compare favorably well with the existing FTIR data.