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Xu K.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Xu K.,Suzhou Nanowin Science and Technology Co. | Wang J.-F.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Wang J.-F.,Suzhou Nanowin Science and Technology Co. | And 2 more authors.
Chinese Physics B | Year: 2015

Three main technologies for bulk GaN growth, i.e., hydride vapor phase epitaxy (HVPE), Na-flux method, and ammonothermal method, are discussed. We report our recent work in HVPE growth of GaN substrate, including dislocation reduction, strain control, separation, and doping of GaN film. The growth mechanisms of GaN by Na-flux and ammonothermal methods are compared with those of HVPE. The mechanical behaviors of dislocation in bulk GaN are investigated through nano-indentation and high-space resolution surface photo-voltage spectroscopy. In the last part, the progress in growing some devices on GaN substrate by homo-epitaxy is introduced. © 2015 Chinese Physical Society and IOP Publishing Ltd. Source


Zeng X.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Han B.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Han B.,University of Chinese Academy of Sciences | Wang X.,Suzhou University of Science and Technology | And 11 more authors.
Journal of Crystal Growth | Year: 2013

Two kinds of GaN powders were grown using the chemical vapor transport process, which involved different Ga sources, i.e., Ga2O3 and Ga metal. Although both GaN powders have a wurtzite crystal structure, which was confirmed by powder X-ray diffraction, their structural and optical properties were different. The powders prepared using the gallium nitridation method revealed a hexagonal morphology. The particles were approximately 2 mm in size, and we determined the large face (0002) by selective area electron diffraction, indicating that they had good crystallinity. In addition, the oxygen content was relatively low, similar to the GaN bulk grown by hydride vapor phase epitaxy. A strong band-edge luminescence was observed in the photoluminescent and cathodoluminescent spectra. However, the powders prepared using the Ga2O3 nitridation method had an irregular morphology, and several tens of nanometer in size. The grain boundaries and the amorphous regions can be seen using high-resolution transmission electron microscopy imaging. Moreover, the oxygen concentration was relatively high. In this paper, we describe the different properties of these two kinds of powders using growth kinetics. © 2013 Elsevier B.V. All rights reserved. Source


Zhang M.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Zhang M.,CAS Institute of Physics | Zhang M.,University of Chinese Academy of Sciences | Zhou T.F.,CAS Suzhou Institute of Nano Technology and Nano Bionics | And 15 more authors.
Applied Physics Letters | Year: 2012

A study on the bound states of Fe impurities in GaN by ultraviolet photoluminescence (PL) emissions is presented. Two elusive PL lines were observed at 3.463 eV (L1) and 3.447 eV (L2), respectively. The intensities of the two lines are proportional to the Fe concentration. The temperature dependence of L1 and L2 revealed acceptor-like and strong localized characteristic, respectively. Furthermore, Raman analysis indicated that L2 is correlated to an exciton bound to a nitride-vacancy (V N) related complex, i.e., [Fe 2+-V N]. By co-doping with Si, the [Fe 2+-V N]-related bound state will enable the spin-coupling between isolated iron ions. © 2012 American Institute of Physics. Source


Zhong H.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Liu Z.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Shi L.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Xu G.,CAS Suzhou Institute of Nano Technology and Nano Bionics | And 8 more authors.
Applied Physics Letters | Year: 2014

The wrinkles of single layer graphene contacted with either n-GaN or p-GaN were found both forming ohmic contacts investigated by conductive atomic force microscopy. The local I-V results show that some of the graphene wrinkles act as high-conductive channels and exhibiting ohmic behaviors compared with the flat regions with Schottky characteristics. We have studied the effects of the graphene wrinkles using density-functional-theory calculations. It is found that the standing and folded wrinkles with zigzag or armchair directions have a tendency to decrease or increase the local work function, respectively, pushing the local Fermi level towards n- or p-type GaN and thus improving the transport properties. These results can benefit recent topical researches and applications for graphene as electrode material integrated in various semiconductor devices. © 2014 AIP Publishing LLC. Source


Zhong H.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Xu K.,CAS Suzhou Institute of Nano Technology and Nano Bionics | Xu K.,Suzhou Nanowin Science and Technology Co. | Liu Z.,CAS Suzhou Institute of Nano Technology and Nano Bionics | And 8 more authors.
Journal of Applied Physics | Year: 2014

Graphene has been proposed as a material for semiconductor electronic and optoelectronic devices. Understanding the charge transport mechanisms of graphene/semiconductor Schottky barriers will be crucial for future applications. Here, we report a theoretical model to describe the transport mechanisms at the interface of graphene and semiconductors based on conventional semiconductor Schottky theory and a floating Fermi level of graphene. The contact barrier heights can be estimated through this model and be close to the values obtained from the experiments, which are lower than those of the metal/semiconductor contacts. A detailed analysis reveals that the barrier heights are as the function of the interface separations and dielectric constants, and are influenced by the interfacial states of semiconductors. Our calculations show how this behavior of lowering barrier heights arises from the Fermi level shift of graphene induced by the charge transfer owing to the unique linear electronic structure. © 2014 AIP Publishing LLC. Source

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