Low temperature growth of AIGaP and GaP on si substrates by atomic layer epitaxy

AIGaP and GaP films were deposited on the (100) Si substrates by atomic layer epitaxy (ALE) in the temperature range between 450 and 600°C. Under optimum growth conditions, the growth of GaP and AIGaP was observed to proceed in a two-dimensional (2-D) fashion in the initial growth stages. These ALE-grown films have better surface morphology when compared with the corresponding MOCVD-grown films. With an AIGaP buffer layer grown on Si, the subsequent growth of GaAs on the AlGaP-coated Si substrates tends to proceed as 2-D growth. This avoids island growth and the two-step growth process currently used.     

Nitrogen vacancy scattering in GaN grown by metal–organic vapor phase epitaxy

Electron mobility limited by nitrogen vacancy scattering was taken into account to evaluate the quality of n-type GaN grown by metal–organic vapor phase epitaxy. Two assumptions were made for this potential for the nitrogen vacancy (1) it acts in a short range, and (2) does not diverge at the vacancy core. According to the above assumptions, a general expression to describe the scattering potential U(r)=−U₀exp[−(r/β)ⁿ], (n=1,2,…,∞) was constructed, where β is the potential well width. The mobilities for n=1,2, and ∞ were calculated based on this equation, corresponding to the simple exponential, Gaussian and square well scattering potentials, respectively. In the limiting case of kβ1 (where k is the wave vector), all of the mobilities calculated for n=1,2, and ∞ showed a same result but different prefactor. Such difference was discussed in terms of the potential tail and was found that all of the calculated mobilities have T^−1/2 temperature and β⁻⁶ well width dependences. A mobility taking account of a spatially complicate scattering potential was studied and the same temperature dependence was also found. A best fit between the calculated results and experimental data was obtained by taking account of the nitrogen vacancy scattering.     

立方相GaN的高温MOCVD生长

利用MOCVD技术在提高生长温度(900℃)下生长出了高质量的立方相GaN,生长速度提高到1.6μm/h.高温生长的GaN样品近带边峰室温光荧光半高宽为48meV,小于在830℃下生长的GaN样品.在ω扫描模式下,X射线衍射表明高温生长的GaN具有较小的(002)峰半高宽21′.可以看出,尽管立方GaN是亚稳态,高生长温度仍然有利于其晶体质量的提高.本文对GaN生长中生长温度和生长速度之间的关系作了讨论.     

Hall effect analysis of high purity p-type GaAs grown by metalorganic chemical vapor deposition

Variable temperature Hall effect and low temperature photoluminescence measurements have been performed on high purityp- andn-type GaAs grown at atmospheric pressure by metalorganic chemical vapor deposition. These high purity epitaxial GaAs layers were grown as a function of the arsine (AsH₃) to trimethylgallium (TMG) ratio (V/III ratio). The accurate quantitative assessment of the electronic properties of thep-type layers was emphasized. Analysis of the material focussed on the variation of the concentration of the shallow impurities for different V/III ratios. Surface and interface depletion effects are included to accurately estimate the concentration of impurities. The model of the merging of the excited states of the acceptor with the valence band is used to include the dependence the activation energy of the impurity on the acceptor concentration as well as on acceptor species identity. The characteristicp- ton-type conversion with increasing V/III ratio was observed in these samples and the reason for thep- ton-type conversion is that the background acceptor concentration of carbon decreases and the germanium donor concentration increases as the V/III ratio is increased.     

Dislocation reduction in gaas grown on Si by MOMBE using multiple indium atomic plane structures

This paper investigates the effectiveness of multiple indium atomic planes in reducing the dislocation density in GaAs epitaxial layers grown by metalorganic molecular beam epitaxy on GaAs-coated Si substrates prepared by metalorganic chemical vapor deposition.In situ reflection high-energy electron diffraction patterns show that, during the growth of multiple indium atomic-plane structures, two-dimensional growth takes place. Cross-sectional transmission electron microscope observation shows that InAs sublayers are commensurate; hence the critical thickness of the InAs layer in this structure is more than one-monolayer. Cathodoluminescence examination indicates that the defect density decreases as the number (<60) of indium atomic planes increases. This new structure is more effective in dislocation reduction than conventional In_0.1Ga_0.9As/GaAs strained-layer superlattices.     

Transmission electron microscopy study of the effect of selenium doping on the ordering of GalnP2

Selenium doped Ga_0.51In_0.49P films have been grown by metalorganic chemical vapour deposition at 600, 670 and 740° C. The extent of ordering of the Group III sublattice has been monitored by transmission electron microscopy. Ordering disappears at carrier concentrations on the order of 10¹⁸ cm⁻³ for samples grown at 600 and 740° C although a small degree of ordering persists in the samples grown at 670° C up to a carrier concentration of 10¹⁹ cm⁻³. At each growth temperature, the ordering observed decreased and the bandgap measured increased with increasing Se doping.     

AlGaAs／AlAs体系DBR的MOCVD生长及表征

设计并利用MOCVD在（311）GaAs衬底上生长了12．5个周期的Al0．6Ga0．4As／AlAs黄绿光分布式Bragg反射（DBR）体系，测量了白光反光谱及其外延片峰值波长分布，反射率90％以上，波长不均匀性在1．0％以下；利用了X射线双晶衍射对其进行结构表征，580nm波长DBR结构周期为84．5nm。     

GaN材料的横向外延过生长(LEO)及其特性研究

对用LEO技术生长GaN材料的选择生长和横向生长速率进行了实验研究。结果表明，作为LEO生长基板的GaN层的表面质量是实现选择生长的关键，而图形方向对横向生长速率与纵向生长速率之比（L／V）也有重要的影响。通过选择合适的工艺条件，实现了GaN材料的LEO外延生长，所得样品的X射线衍射峰宽比用常规MOCVD法生长的样品减小了1／3。     

976 nm高效率半导体激光器

976 nm高效率半导体激光器是这几年研究的热点,在固体激光器泵浦领域有广阔的应用。通过优化半导体激光器材料外延结构中包覆层和波导层的铝组分,降低了工作电压;通过采用微通道水冷系统,并进行优化降低了热阻,从而提高了室温下的电光转换效率。25℃室温连续测试条件下,1 cm的线阵列(巴条),2 mm腔长,50%填充因子,在110 A下,出光功率为114.2 W,电压为1.46 V,电光转换效率为71%。15条微通道封装成的垂直叠阵,进行光束整形后,获得了室温976 nm连续输出功率1 500 W,电光转换效率大于70%。     

用于制备YBCO薄膜的光辅助MOCVD反应器内流动现象的数值研究

对一种制备YBCO薄膜的光辅助MOCVD反应器内的流动现象进行了三维数值模拟研究.在模拟计算中,分别改变基座与进口的相对角度(Φ)、反应器顶壁倾斜角度(Ψ),得出反应器中流场的相应变化.根据对模拟结果的分析,发现当基座平面与进气口轴线之间的夹角Φ=22.5°及反应器顶壁倾角ψ=30°时,基片表面气流速度大小合适,分布均...