GROWTH OF WIDE-BAND GAP IMMISCIBLE II-VI ALLOYS BY METALORGANIC VAPOR-PHASE EPITAXY

Although metalorganic vapor phase epitaxy (MOVPE) is generally regarded as a non-equillibrium process, it can be assumed that a chemical equilibrium is established at the vapor-solid interface in the diffusion limited region of growth rate. In this paper, an equilibrium model was proposed to calculate the relation between vapor and solid compositions for II-VI ternary alloys. Metastable alloys in the miscibility gap may not be obtained when the growth temperature is lower than the critical temperature of the system. The influence of growth temperature, reactor pressure, input VI/II ratio, and input composition of group VI reactants has been calculated for ZnSSe, ZnSeTe and ZnSTe. The results are compared with experimental data for the ZnSSe and ZnSTe systems.

1ST-PRINCIPLES CALCULATIONS FOR QUASI-PARTICLE ENERGIES OF GAP AND GAAS

We have applied the Green-function method in the GW approximation to calculate quasiparticle energies for the semiconductors GaP and GaAs. Good agreement between the calculated excitation energies and the experimental results was achieved. We obtained calculated direct band gaps of GaP and GaAs of 2.93 and 1.42 eV, respectively, in comparison with the experimental values of 2.90 and 1.52 eV, respectively. An ab initio pseudopotential method has been used to generate basis wave functions and charge densities for calculating the dielectric matrix elements and self-enegies. To evaluate the dynamical effects of the screened interaction, the generalized-plasma-pole model has been utilized to extend the dielectric matrix elements from static results to finite frequencies. We presen the calculated quasiparticle energies at various high-symmetry points of the Brillouin zone and compare them with the experimental results and other calculations.

Growth of GaN layers on GaAs and GaP (111) and (001) substrates by molecular beam epitaxy

Films of GaN have been grown using a modified MBE technique in which the active nitrogen is supplied from an RF plasma source. Wurtzite films grown on (001) oriented GaAs substrates show highly defective, ordered polycrystalline growth with a columnar structure, the (0001) planes of the layers being parallel to the (001) planes of the GaAs substrate. Films grown using a coincident As flux, however, have a single crystal zinc-blende growth mode. They have better structural and optical properties. To improve the properties of the wurtzite films we have studied the growth of such films on (111) oriented GaAs and GaP substrates. The improved structural properties of such films, assessed using X-ray and TEM method, correlate with better low-temperature FL.

Study of intensity-dependent nonlinear optical coefficients of GaP optical crystal at 800 nm by femtosecond pump-probe experiment

The intensity-dependent two-photon absorption and nonlinear refraction coefficients of GaP optical crystal at 800 nm were measured with time-resolved femtosecond pump-probe technique. A nonlinear refraction coefficient of 1.7*10^(-17) m2/W and a two-photon absorption coefficient of 1.5*10^(-12) m/W of GaP crystal were obtained at a pump intensity of 3.5*10^(12) W/m2. The nonlinear refraction coefficient saturates at 3.5*10^(12) W/m2, while the two-photon absorption coefficient keeps linear increase at 6*10^(12) W/m2. Furthermore, fifth-order nonlinear refraction of the GaP optical crystal was revealed to occur above pump intensity of 3.5*10^(12) W/m2.

纳米碳管模板法制取的GaP纳米棒拉曼光谱研究

报道了用纳米碳管模板法制备的GaP纳米棒的拉曼光谱特征，观测到声子限制效应引起的GaP纳米棒TO和LO模的红移，红移量一般在2－10cm^-1之间，与所测到的纳米棒的尺寸有关，在偏振特性研究中，发现GaP纳米棒的偏振特性不能用单根纳米棒的选择定则来解释，而与测量光斑内多根纳米棒的无序取向有关，无序程度越高，偏振特性的方向性越弱，当激发光功率增加时，GaP纳米棒的TO和LO模的频率显著减少，表明纳米棒中的激光加热效应比体材料中强很多，而且GaP纳米棒的拉曼散射强度随激发光功率的增加先饱和，然后减小，表明在强激发功率下GaP纳米棒中的缺陷会迅速增加。

GaP∶NLPE片的纵向载流子浓度分布

于2010-11-23批量导入

GS-MBE生长的GaP/Si的XPS研究

利用X射线光电子能谱(XPS)深度剖析方法对气体源分子束外延(GS-MBE)生长的GaP/Si异质结构进行了详细的分析。其结果表明

Ni＋注入n-GaP DLTS谱中Ni杂质能级的识别

在不同条件下退火的Ni~+注入n-GaP DLTS谱中观测到表观激活能在0.60～0.70eV范围内的多个多子峰和少子峰。对各样品掺杂层内的能带弯曲及Ni杂质各荷电状态浓度空间分布在DLTS测量的零偏-反偏过程中的变化进行了计算。结合分析实测各能级热发射率数据,对其中起源于Ni_(Ga)中心的DLTS峰作出了判断。