Temperature dependent dielectric studies of Ni/n-GaP Schottky diodes by capacitance and conductance measurements

The dielectric properties of Ni/n-GaP Schottky diode were investigated in the temperature range 140–300 K by capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements. The effect of temperature on series resistance (R_s) and interface state density (N_ss) were investigated. The dependency of dielectric constant (ε′), dielectric loss (ε′′), loss tangent (tan δ), ac conductivity (σ_ac), real (M′) and imaginary (M′′) parts of the electric modulus over temperature were evaluated and analyzed at 1 MHz frequency. The temperature dependent characteristics of ε′ and ε′′ reveal the contribution of various polarization effects, which increases with temperature. The Arrhenius plot of σ_ac shows two activation energies revealing the presence of two distinct trap states in the chosen temperature range. Moreover, the capacitance–frequency (C–f) measurement over 1 kHz to 1 MHz was carried out to study the effect of localized interface states.     

Structural and optical characterization of self-formed GaP/InP quantum dots

By growing (GaP)_1.5(InP)_1.88 and (InP)_1.88(GaP)_1.5 short-period superlattices (the former material is the first layer on the GaAs (311) substrate) by gas source MBE, composition-modulated quantum dots were self-formed in both cases. The dot size is about 20 nm in GaP/InP and 22 nm in InP/GaP sample. The photoluminescence energy is higher for the GaP/InP sample, corresponding to the difference in the dot size. The photoluminescence decay time of the InP/GaP sample is less dependent on the emission wavelength and temperature than that of the GaP/InP sample.     

The Characteristics of GaP Window Layer Grown by Indium‐added Liquid Phase Epitaxy

The effects of added Indium on the growth characteristics of GaP were systematically studied using conventional liquid phase epitaxy technique with Ga‐rich GaP source melt. The GaP growth rate uniformly increase with the source melt of increasing Indium addition against Gallium solvent. These epilayers have mirror‐like surface morphology examined by optical microscope except several grown films with large amount of Indium addition meet a terrible interface. The surface morphologies examined by AFM showed the ripples in samples of R_0.05 and R_0.4 and distinct islands with elliptical base shape in the sample of R_0.7 (R‐In ratio). The epitaxial layer with incorporation of Indium addition during growth had good performance on the carrier concentrations and resistivity. The composition of compound semiconductor become to InGaP at higher amount of In addition to Ga was examined by double‐crystal X‐ray diffraction and the distribution of Indium examined by SIMS also provided the evidences in sample of R_0.7.     

Overcoming limitations in semiconductor alloy design

The phenomenon of giant band gap ‘bowing’ recently observed in several III–V dilute nitride alloys is promising for increasing the flexibility in choice of semiconductor band gaps available for specified lattice constants. However, the poor electrical transport properties that these materials exhibit seriously limit their usefulness. It is proposed that these materials behave as heavily nitrogen-doped semiconductors rather than dilute nitride alloys and that the abnormal or irregular alloy behavior is associated with impurity band formation that manifests itself in the giant bowing and poor transport properties. The potential for regularizing the alloy behavior using isoelectronic co-doping is discussed.     

纳米GaP材料Ga填隙缺陷的EPR实验观察

利用电子顺磁共振(EPR)技术对纳米GaP粉体材料的本征点缺陷进行了研究，结果表明：由EPR信息的g因子值（2.0027±0.0004）可以确定纳米GaP粉体材料存在Ga自填隙（Ga_i）本征缺陷；纳米GaP粉体EPR信号超精细结构消失，以及谱线线宽（ΔH_PP）变窄等实验现象，可能是由纳米材料界面的无序性，以及缺陷原子和界面原子之间的电子交换造成的；在较低的测试温度范围内，升高温度引起纳米GaP材料发生晶界结构弛豫；当测试温度由100 K升高至423 K时，ΔH_PP值和自由基浓度皆逐渐降低.     

Bromine ion-beam-assisted etching of III–V semiconductors

Bromineion-beam-assisted etching produces smooth vertical sidewalls in GaAs, GaP, InP, AlSb, and GaSb as well as in the usual alloys formed from these materials. Care must be taken, however, during etching to match the specific material system with an appropriate substrate etch temperature. For example, vertical walls were obtained using substrate temperatures in the range of 150 to 200°C with InP, 80 to 140°C with GaAs and GaP, and below 30°C with AlSb and GaSb. GaN has also been etched with the technique. Our etching experience and the vapor pressure data for bromine with group III and group V elements lead us to believe that all of the various technologically important III-V binaries, ternaries, and quaternaries can be etched. Etch rates of most of the materials can be varied from several nm/min to 0.16 μm/min through the bromine flow rate, Ar⁺ ion beam density and energy, and the substrate temperature. Bromine ion-beam-assisted etching also appears to have an advantage over chlorine ion-beam-assisted etching in many situations, in that substrate temperature ranges can be found for which vertical sidewalls are maintained while etching through layered structures composed of various alloys of the materials. Here we present results obtained from etching a number of III-V binaries, alloys, and heterostructures.     

基于Mie散射理论的磷化镓粒子散射特性

基于Mie散射理论,对磷化镓微球粒子从紫外光区到红外光区的光散射特性进行了数值计算与理论分析,得到了散射强度与散射角、粒子尺寸参数、偏振度与散射角以及光学截面与粒子尺寸参数的关系。结果表明,入射波长越长,粒子半径越小,散射越弱;并且在红外波段光散射很弱,在散射角90°方向上能观测到线偏振光,这为磷化镓材料的制备与应用提供了理论参考。     

InP quantum dots in (1 0 0) GaP: Growth and luminescence

We describe the growth and optical emission from strained InP quantum wells and quantum dots grown on GaP substrates using gas-source molecular beam epitaxy. Self-organized quantum dot formation takes place for InP coverage greater than 1.8 monolayers on the (1 0 0) GaP surface. Atomic force and scanning-electron microscopy studies indicate that unburied dots have a lateral size of 60–100 nm and are about 20 nm high, with dot densities in the range of 2–6×10⁸ cm⁻² for InP coverage between 1.9 and 5.8 MLs. Intense photoluminescence is emitted from both the quantum wells and the quantum dots at energies of about 2.2 and 2.0 eV, respectively. Time-resolved measurements indicate rather long carrier lifetimes of about 19 ns in the quantum wells and about 3 ns in the quantum dots. The data indicate that the InP/GaP quantum wells form a type-II band system, with electrons in the X valleys of the GaP recombine with holes in the InP. Furthermore, in the InP/GaP quantum dot system, the conduction band edge in the X valley of the GaP is nearly aligned with that in the Γ valley of the InP. Rapid thermal annealing of the quantum dots results in at least a six-fold enhancement of integrated emission intensity as well as some Ga-In interdiffusion. The low interdiffusion activation energy indicates that the material near the interface between the GaP matrix and the InP dots is not free of defects.     

LED-GaP外延晶片洁净优化技术的研究

介绍了绿色,红色发光ＧａＰ外延晶片不同发光强度的无损检测方法。分别用短紫外光和蓝光激发方式,在室温下,有效地观测了ＬＥＤ－ＧａＰ：Ｎ的多峰ＰＬ谱。根据对上述两种发光ＧａＰ外延晶片的相对光强与金属杂质Ｆｅ,Ｃｕ,Ｎｉ和Ｃｒ紫外荧光谱的实测数据的相关性,讨论了ＬＥＤ－ＧａＰ外延晶片的工艺质量优化和洁净度的问题。     

频率分辨双光束耦合抽运-探测技术中的空间效应研究

在测量非线性折射率和双光子吸收系数的频率分辨双光束耦合抽运 探测技术中 ,光场的空间分布没有得到考虑。研究了入射飞秒光脉冲的空间分布对实验结果的影响。对不同部位的探测光进行测量可以得到完全不同的结果 ,用所发展的理论给出了解释。通过数值拟合获得了磷化镓 (GaP)在飞秒激光脉冲作用下的非线性折射率和双光子吸收系数。进一步可能从实验上主动选择适当的空间滤波来获得频率 空间分辨信号。