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Zhang J.C.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | Liu F.Q.,CAS Institute of Semiconductors | Yao D.Y.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | Zhuo N.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | And 3 more authors.
Journal of Applied Physics | Year: 2013

A novel index-coupled distributed feedback quantum cascade laser emitting at λ ∼ 4.8 μm is demonstrated by a sampled grating. The coupling coefficient can be almost controlled arbitrarily according to the duty cycle of sampled grating. The additional supermodes caused by the sampled grating can be strongly suppressed by choosing a small sampling period, so that the supermodes are shifted apart from the gain curve. Single-mode emission without any significant disadvantages compared with uniform grating is achieved. Especially, this powerful approach presented here can be applied to achieve the performance with high power and low threshold simultaneously. © 2013 AIP Publishing LLC. Source


Li W.,CAS Institute of Semiconductors | Wang X.,CAS Institute of Semiconductors | Wang X.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | Wang X.,ISCAS XJTU Joint Laboratory of Functional Materials and Devices for Informatics | And 7 more authors.
Journal of Alloys and Compounds | Year: 2014

The high electron mobility transistor (HEMT) structure employing novel InxAl1-xN/AlN multiple-quantum-wells (MQWs) as barrier layer is presented. The two-dimensional electron gas (2DEG) characteristics of (InxAl1-xN/AlN) MQWs/GaN heterojunction have been investigated by solving coupled Schrödinger and Poisson equations self-consistently. The influence of AlN thickness, InxAl1-xN thickness, In content and pair number of (InxAl1- xN/AlN)MQWs on sheet carrier density is investigated. AlN thickness dependence of carriers in barrier layer to total carriers in HEMT and In 0.18Al0.82N conduction band diagrams are discussed. The sheet carrier density of (In0.18Al0.82N/AlN)MQWs/GaN heterojunction is larger than that of (AlxGa1 -xN/GaN)SLs/GaN heterojunction and achieves to as large as 3.59 × 1013 cm-2 with AlN thickness of 1.4 nm, barrier thickness of 15 nm and pair number of 5. The calculation shows that (In0.18Al0.82N/AlN)MQWs provide high barrier which confines the 2DEG effectively. © 2014 Elsevier B.V. All rights reserved. Source


Peng E.,CAS Institute of Semiconductors | Wang X.,CAS Institute of Semiconductors | Wang X.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | Wang X.,ISCAS XJTU Joint Laboratory of Functional Materials and Devices for Informatics | And 10 more authors.
Journal of Applied Physics | Year: 2013

This is a theoretical study of GaN-based heterostructures with unintentionally doped (UID) GaN channel layer and high-resistivity (HR) GaN buffer layer doped by deep acceptors. Self-consistent Schrödinger-Poisson (SP) numerical simulation shows that, by increasing the acceptor concentration in the HR buffer or narrowing the width of UID channel, the quantum confinement of two-dimensional electron gas (2DEG) is enhanced, while the sheet density of 2DEG is reduced. The tuning effect of 2DEG density is attributed to the depletion effect of negative space charges composed of ionized acceptors located in the region between the UID channel and the Fermi-level pinned region in the HR buffer. For the heterostructure without the UID channel, the 2DEG can be depleted as the acceptor concentration is beyond a critical value. However, by inserting a UID channel layer, the depletion effect of buffer acceptor on 2DEG density is reduced. To gain a further insight into the physics, a simple analytical model is developed, which reproduces well the results of SP simulation. By comparing our theoretical results with the experimental ones, a good agreement is reached, thus the validity of our model is verified. © 2013 AIP Publishing LLC. Source


Kang H.,CAS Institute of Semiconductors | Wang Q.,CAS Institute of Semiconductors | Xiao H.-L.,CAS Institute of Semiconductors | Wang C.-M.,CAS Institute of Semiconductors | And 10 more authors.
Chinese Physics Letters | Year: 2014

Lateral Schottky barrier diodes (SBDs) on AlGaN/GaN heterojunctions are fabricated and studied. The characteristics of the fabricated SBDs with different Schottky contact diameters and different Schottky-Ohmic contact spacings are investigated. The breakdown voltage can be increased by either increasing the Schottky-Ohmic contact spacing or increasing the Schottky contact diameter. However, the specific on-resistance is increased at the same time. A high breakdown voltage of 1400 V and low reverse leakage current below 20nA are achieved by the device with a Schottky contact diameter of 100 μm and a contact spacing of 40 μm, yielding a high V2BR/RON,sp value of 194 MW.cm-2. © 2014 Chinese Physical Society and IOP Publishing Ltd. Source


Chen T.,CAS Institute of Semiconductors | Chen T.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | Zhao Y.,CAS Institute of Semiconductors | Zhao Y.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | And 6 more authors.
Materials Letters | Year: 2013

CuIn1-xGaxSe2 (CIGS) compounds used for the fabrication of thin-film solar cell absorber layers have been synthesized by a novel melting method which is easily controlled and practical. Based on vapor phase transport caused by the temperature gradient built, the quaternary CIGS alloy was prepared from the low-cost elementary Cu, In, Ga and Se in a closed quartz tube at 1100 C for 3 h. Through various characterization methods, the as-synthesized alloy with crystal grains sized 100-150 μm presented a desirable chemical composition and a single-phase chalcopyrite structure. Furthermore, the CIGS absorber layer made from this material turned out to be high-quality with a correct phase and large nanocrystals, indicating great application potential of the proposed method in low-cost solar cell fabrication. © 2013 Elsevier B.V. Source

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