2016年9月26日星期一

Photoluminescence assessment of undoped semi-insulating InP wafers obtained by annealing in iron phosphide vapour

We have investigated the photoluminescence mapping characteristics of semi-insulating (SI) InP wafers obtained by annealing in iron phosphide ambience (FeP2-annealed). Compared with as-grown Fe-doped and undoped SI InP wafers prepared by annealing in pure phosphorus vapour (P-annealed), the FeP2-annealed SI InP wafer has been found to exhibit a better photoluminescence uniformity. Radial Hall measurements also show that there is a better resistivity uniformity on the FeP2-annealed SI InP wafer. When comparing the distribution of deep levels between the annealed wafers measured by optical transient current spectroscopy, we find that the incorporation of iron atoms into the SI InP suppresses the formation of a few defects. The correlation observed in this study implies that annealing in iron phosphorus ambience makes Fe atoms diffuse uniformly and occupy the indium site in the SI InP lattice. As it stands, we believe that annealing undoped conductive InP in iron phosphide vapour is an effective means to obtain semi-insulating InP wafers with superior uniformity.

Keywords:  photoluminescence ;  semi-insulating (SI) InP wafers;  phosphide ambience (FeP2-annealed);  SI InP wafers;  semi-insulating InP wafers

Source: Iopscience

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2016年9月19日星期一

Semicoherent growth of Bi$_{2}$Te$_{3}$ layers on InP substrates by hot wall epitaxy

We search for optimum growth conditions to realize flat Bi$_{2}$Te$_{3}$ layers on InP(111)B by hot wall epitaxy. The substrate provides a relatively small lattice mismatch, and so (0001)-oriented layers grow semicoherently. The temperature window for the growth is found to be narrow due to the nonzero lattice mismatch and rapid re-evaporation of Bi$_{2}$Te$_{3}$. The crystalline qualities evaluated by means of x-ray diffraction reveal deteriorations when the substrate temperature deviates from the optimum not only to low temperatures but also to high temperatures. For high substrate temperatures, the Bi composition increases as Te is partially lost by sublimation. We show, in addition, that the exposure of the Bi$_{2}$Te$_{3}$ flux at even higher temperatures results in anisotropic etching of the substrates due, presumably, to the Bi substitution by the In atoms from the substrates. By growing Bi$_{2}$Te$_{3}$ layers on InP(001), we demonstrate that the bond anisotropy on the substrate surface gives rise to a reduction in the in-plane epitaxial alignment symmetry.

Keywords:   InP(001);  Bi$_{2}$Te$_{3}$;  Bi substitution;  

Source: iopscience

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2016年9月11日星期日

Investigation of room-temperature wafer bonded GaInP/GaAs/InGaAsP triple-junction solar cells

Highlights

•High quality InGaAsP material with a bandgap of 1.0 eV was grown by MBE.
•Room-temperature wafer-bonded GaInP/GaAs/InGaAsP SCs were fabricated.
•An efficiency of 30.3% of wafer-bonded triple-junction SCs was obtained.

We report on the fabrication of III–V compound semiconductor multi-junction solar cells using the room-temperature wafer bonding technique. GaInP/GaAs dual-junction solar cells on GaAs substrate and InGaAsP single junction solar cell on InP substrate were separately grown by all-solid state molecular beam epitaxy (MBE). The two cells were then bonded to a triple-junction solar cell at room-temperature. A conversion efficiency of 30.3% of GaInP/GaAs/InGaAsP wafer-bonded solar cell was obtained at 1-sun condition under the AM1.5G solar simulator. The result suggests that the room-temperature wafer bonding technique and MBE technique have a great potential to improve the performance of multi-junction solar cell.

Graphical abstract

Image for unlabelled figure

Keywords:  Multijunction solar cell;  GaInP/GaAs/InGaAsP;  Room-temperature wafer bonding;  Molecular beam epitaxy

Source: Sciencedirect

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Monolithic of SOI wafer waveguide and InP-laser with DVS-BCB coating and bonding

Highlights

•DVS-BCB polymer is investigated as a new material for silicon photonic chips' binding.
•The bonding layer is considered to having high transmittance (> 90%), and high temperature thermal stability.
•DVS-BCB polymer has the merits of low relative dielectric constant, lower baking temperature, and high optical clarity.
•DVS-BCB polymer films are easily produced using simple resist spin track equipment.

Si photonic is an optical information processing technology, including lasers, optical modulators, waveguide and a photodetector, and the light signal is performed by a basic photonic systems. In silicon microelectronics world, hundreds of millions of pieces of single components are integrated into a single platform to “parallel manufacturing” approach at the same time, the current optical transmission systems, the main technology is based on an independent element “series mode” manufacturing. Bonding technology is becoming realized comprising laser, an optical modulator, a waveguide and a photodetector system integration. Several conventional bonding methods have been developed a practical method. Wherein, the silicon substrate and the III–V group bonding, does not need to atomically smooth surface engagement, and the conventional bonding method is comparison with great flexibility, allowing the binding material or structure of the highest quality. Silicon has a high thermal conductivity and low light absorption, and the properties of these two substances silicon photonic application is very advantageous. Relatively low cost and high quality SOI wafers, making them an ideal platform to create a CMOS-compatible planar waveguide circuits. In this research, we focus on BCB coating, bonding, and adhesion observation for monolithic SOI wafer waveguide and InP-laser. The IV (Current–voltage) curve measured under the needle was found operating under current of approximately 8 mA at 1.5 V, LI (Optical power-Current) measurement results found at 36 mA operating maximum optical power of about 1.2 mW. This method owns the advantages of simple fabrication process, great performance and high adhesion efficient between BCB layer and Si waveguide.

Graphical abstract

Image for unlabelled figure

Keywords:  Silicon;  Waveguide;  InP-laser;  BCB coating

Source: Sciencedirect

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