Optical and structural properties of InGaAs/InP double quantum wells grown by molecular beam epitaxy with polycrystalline GaAs and GaP decomposition sources

We report successful growth of high-quality InGaAs/InP double quantum wells (DQWs) with safer and more cost-effective decomposition source molecular beam epitaxy (MBE). The transmission electron microscopy (TEM) images and double crystal X-ray diffraction (TCXD) measurement reveal the formation of abrupt interfaces between InGaAs and InP layers. In the case of optical quality, the line width of 12 K-photoluminescence of the DQWs is 8.2 meV, which is comparable to that of single quantum well grown by MBE with PH₃ cracker and more complex instrument (4 meV).     

Growth of wide band gap wurtzite ZnMgO layers on (0001) Al2O3 by radical-source molecular beam epitaxy

Wurtzite structure ZnMgO layers have been grown using radical-source molecular beam epitaxy on high-quality ZnO buffer layers grown on (0001) sapphire substrates. The thickness of the ZnO buffer layers is 300 nm, with full width at half maxim of the HR-XRD (0002) rocking curves as low as 25 arcsec. In-situ Reflection High-Energy Electron Diffraction (RHEED) was employed for the optimization of the ZnMgO growth. RHEED and X-Ray Diffractometry measurements did not reveal any phase change from the wurzite structure to the rocksalt structure. The C-lattice parameter of Zn_1−xMg_xO films decreased from 5.209 to 5.176 Å with increasing x to 0.2. The surface morphology of the samples was studied with atomic force microscopy. The root mean square roughness values of 200 nm thick ZnMgO (x=0.2) was less than 1 nm. The main photoluminescence peak of Zn_1−xMg_xO shifted to as high as 3.77 eV owing to the increasing Mg composition of up to x=0.2.     

Evolution of InAs islands in the Stranski-Krastanow mode of InAs/GaAs(001) fabricated using molecular beam epitaxy

Based on step-by-step observation using atomic force microscope, two distinctive successive phases were distinguished in accordance with evolution of the three-dimensional InAs islands during the Stranski-Krastanow mode of the InAs/GaAs(001) system fabricated using molecular-beam epitaxy. The initial phase is consistent with a power law, and the latter phase is a comparatively gradual one.      

原位等离子体逐层氧化a-Si:H/SiO2多层膜的光致发光研究

采用在等离子体增强化学汽相沉积系统中沉积a-Si:H和原位等离子体逐层氧化的方法制备a-Si:H/SiO2多层膜.改变a-Si:H层的厚度，首次在室温下观察到来自a-Si:H/SiO2多层膜较强的蓝色光致发光和从465到435nm的蓝移.x射线能谱证明，SiO2层是化学配比的SiO2；C-V特性表明，a-Si:H/SiO2界面得到了很好的钝化；透射电子显微镜表明，样品形成了界面陡峭的多层结构.结合光吸收谱和光致发光谱的研究，对其发光机理进行了讨论.用一维量子限制模型对光致发光峰随着a-Si:H层厚度的减小 关键词： a-Si:H/SiO2多层膜 光致发光     

1.3 μm range effectively cylindrical In0.53Ga0.47As/In0.52Al0.48As quantum wires grown on (2 2 1)A InP substrates by molecular beam epitaxy

Vertically coupled quantum wires (QWRs) have been made by alternately stacking nominally 3.6 nm thick In_0.53Ga_0.47As self-organized QWR layers and 1 nm thick In_0.52Al_0.48As barrier layers on (2 2 1)A-oriented InP substrates by molecular beam epitaxy. The surface of In_0.53Ga_0.47As QWR layers was corrugated at an amplitude of 1.1 nm and period of 27 nm, and lateral confinement potential is induced by their thickness modulation. The wavelength of photoluminescence (PL) from the stacked QWRs at 15 K becomes longer from 1220 to 1327 nm with increasing total number of stacked QWR layers, N_SL, from 1 to 9, while PL full-width at half-maximum is reduced from 22 to 8.6 meV. The PL intensity with the polarization parallel to the wire direction, I, is 1.30 times larger than that with the normal polarization, I, when N_SL=1. The PL intensity ratio, I/I, reaches as large as 4 when N_SL=9, indicating successful control of relative strength between vertical confinement and lateral confinement of carriers. The value of I/I obtained for the stacked QWRs with N_SL=9 is the same value as cylindrical QWRs have. The results indicate that effectively cylindrical QWRs with the best uniformity and 1.3 μm range emission were realized by stacking of self-organized QWR layers.