InP的MOVPE生长

利用常压MOVPE设备和国产的三甲基铟以及进口的磷烷生长了InP处延材料,其77K迁移 率为65300cm~2/V·s,是国内迄今为止用各种方法获得的InP薄膜的最大低温迁移率值.

ZnSe的MOVPE生长相图以DMZn和H2Se为源

基于热力学平衡计算,首次给出以DMZn和H_2Se为源,MOVPE生长ZnSe的相图.文中讨论了ZnSe单一凝聚相区的范围,以及可能出ZnSe(s)+Zn(s)或ZnSe(s)+Se(1)两种双凝聚相区的条件.

GaN的MOVPE生长和m-i-n型蓝光LED的试制

国家863计划

注入电流对于MOVPE生长GaAs薄层光透射特性的影响

于2010-11-23批量导入

MOVPE生长GaAs薄层的线偏振光吸收系数的电流感生变化

于2010-11-23批量导入

Yellow luminescence mechanism and persistent photoconductivity in n-GaN single crystal films grown on alpha-Al2O3(0001) substrates by LP-MOCVD

Unintentionally doped and Si-doped single crystal n-GaN films have been grown on alpha-Al2O3 (0001) substrates by LP-MOCVD. Room temperature photoluminescence measurement showed that besides the bandedges, the spectrum of an undoped sample was a broad deep-level emission band peaking from 2.19 to 2.30eV, whereas the spectrum for a Si-doped sample was composed of a dominant peak of 2.19eV and a shoulder of 2.32eV. At different temperatures, photoconductance buildup and its decay were also observed for both samples.. The likely origins of persistent photoconductivity and yellow luminescence, which might be associated with deep defects inclusive of either Ga vacancy(V-Ga)/Ga vacancy complex induced by impurities or N antisite (N-Ga), will be proposed.

Growth of Fe doped semi-insulating InP by LP-MOCVD

The semi-insulating InP has been grown using ferrocene as a dopant source by low pressure MOCVD. Fe doped semiinsulating InP material whose resistivity is equal to 2.0x10(8)Omega*cm and the breakdown field is Beater than 4.0x10(4)Vcm(-1) has been achieved. It is found that the magnitude of resistivity increases with growing pressure enhancement under keeping TMIn, PH3, ferrocene (Fe(C5H5)(2)) flow constant at 620 degrees C growth temperature. Moreover, the experimental results which resistivity varies with ferrocene mole fraction are given. It is estimated that active Fe doping efficiency; eta, is equal to 8.7x10(-4) at 20mbar growth pressure and 620 degrees C growth temperature by the comparison of calculated and experimental results.

The effect of low temperature GaAs nucleation on the growth of GaN on Silicon (001) during MOVPE process

High quality cubic GaN was grown on Silicon (001) by metalorganic vapor phase epitaxy (MOVPE) using a GaAs nucleation layer grown at low temperature. The influence of various nucleation conditions on the GaN epilayers' quality was investigated. We found that the GaAs nucleation layer grown by atomic layer epitaxy (ALE) could improve the quality of GaN films by depressing the formation of mixed phase. Photoluminescence (PL) and X-ray diffraction were used to characterize the properties of GaN epilayers. High quality GaN epilayers with PL full width at half maximum (FWHM) of 130meV at room temperature and X-ray FWHM of 70 arc-min were obtained by using 10-20nm GaAs nucleation layer grown by ALE.

High temperature operation of 650nm AlGaInP quantum well laser diodes grown by LP-MOCVD

Low threshold current and high temperature operation of 650nm AlGaInP quantum well laser diodes grown by low pressure metal organic chemical vapor deposition (LP-MOCVD) are reported in this paper. 650nm laser diodes with threshold current as low as 22-24mA at room temperature, and the operating temperature over 90 degrees C at CW output power 5 mW were achieved in this study. These lasers are stable during 72 hours burn in under 5mW at 90 degrees C.

Visible vertical cavity surface emitting laser

We have designed and fabricated the visible vertical-cavity surface-emitting lasers (VCSEL's) by using metalorganic vapor phase epitaxy (MOVPE). We use the 8 lambda optical cavities with 3 quantum wells in AlGaInP/AlGaAs red VCSEL's to reduce the drift leakage current and enhance the model gain in AlGaInP active region. The structure has a p-type stack with 36 DBR pairs on the top and an n-type with 55-1/2 pairs on the bottom. Using micro-area reflectance spectrum, we try to get a better concordance between the center wavelength of DBR and the emitting wavelength of the active region. We used a component graded layer of 0.05 lambda thick (x = 0.5 similar to 0.9) at the p-type DBR AlGaAs/AlAs interface to reduce the resistance of p-type DBR. We use selective oxidation to define the current injection path. Because the oxidation rate of a thick layer is faster than a thinner one, we grown a thick AlAs layer close to the active region. In this way, we got a smaller active region for efficient confinement of injected carriers (the aperture area is 3 x 3 mu m) to reduce the threshold and, at the same time, a bigger conductive area in the DBR layers to reduce the resistance. We employ Zn doping on the p-side of the junction to improve hole injection and control the Zn dopant diffusion to get proper p-i-n junction. At room temperature, pulse operation of the laser has been achieved with the low threshold current of 0.8mA; the wavelength is about 670nm.

MOVPE growth of GaN and LED on (111) MgAl2O4

The growth of wurtzite GaN by low-pressure metalorganic vapor-phase epitaxy on (1 1 1) magnesium aluminate (MgAl2O4) substrates have been studied. The morphological, crystalline, electrical and optical properties are investigated. A p-n junction GaN LED was fabricated on the MgAl2O4 substrate. (C) 1998 Elsevier Science B.V. All rights reserved.

长白山赤杨丛枝菌根真菌多样性的半巢式LP-PCR-SSCP检测分析

利用半巢式LP PCR SSCP技术 ,对中国吉林长白山不同海拔生境下 3种赤杨共生丛枝菌根真菌的多样性进行检测分析 .结果表明 ,该地区赤杨属东北赤杨、西伯利亚赤杨及色赤杨共生丛枝菌根真菌在科乃至种的水平上并未随宿主的变化表现出丰富的多样性 ;3个树种在自身属的水平上与共生的球囊霉科 (Glomaceae)至少 1种AMF ,即G .intraradix ,在种的水平上表现出不相关于宿主海拔高度的某种相互选择性 .

Effects of Subgrid-Scale Modeling on Time Correlations in Large Eddy Simulation

The effects of the unresolved subgrid-scale (SGS) motions on the energy balance of the resolved scales in large eddy simulation (LES) have been investigated actively because modeling the energy transfer between the resolved and unresolved scales is crucial to constructing accurate SGS models. But the subgrid scales not only modify the energy balance, they also contribute to temporal decorrelation of the resolved scales. The importance of this effect in applications including the predictability problem and the evaluation of sound radiation by turbulent flows motivates the present study of the effect of SGS modeling on turbulent time correlations. This paper compares the two-point, two-time Eulerian velocity correlation in isotropic homogeneous turbulence evaluated by direct numerical simulation (DNS) with the correlations evaluated by LES using a standard spectral eddy viscosity. It proves convenient to express the two-point correlations in terms of spatial Fourier decomposition of the velocity field. The LES fields are more coherent than the DNS fields: their time correlations decay more slowly at all resolved scales of motion and both their integral scales and microscales are larger than those of the DNS field. Filtering alone is not responsible for this effect: in the Fourier representation, the time correlations of the filtered DNS field are identical to those of the DNS field itself. The possibility of modeling the decorrelating effects of the unresolved scales of motion by including a random force in the model is briefly discussed. The results could have applications to the problem of computing sound sources in isotropic homogeneous turbulence by LES