Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices

Beijing, China

Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices

Beijing, China

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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.


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.


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.


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.


Zhang J.-C.,CAS Institute of Semiconductors | Zhang J.-C.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | Yao D.-Y.,CAS Institute of Semiconductors | Yao D.-Y.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | And 12 more authors.
Applied Physics Letters | Year: 2014

We report a beam reshaping phenomena via nanopore array defined on the emission window of a substrate emitting quantum cascade lasers. A pronounced beam divergence reduction by a factor of 6 in the elongated beam direction is achieved. A collimated laser beam with small divergence (2.9°×0. 12°) is observed. These single-mode devices preserve good power and spectral performances at room temperature continuous wave operation. This beam reshaping design is simple to fabricate and able to be adapted for other wavelengths ranging from the visible to mid-infrared regimes, which would open up major opportunities for the control of beam divergence. © 2014 AIP Publishing LLC.


Zhang J.C.,CAS Institute of Semiconductors | Zhang J.C.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | Liu F.Q.,CAS Institute of Semiconductors | Liu F.Q.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | And 10 more authors.
Journal of Applied Physics | Year: 2014

A novel surface emitting distributed feedback quantum cascade laser emitting around λ ∼ 4.6 μm is demonstrated by employing an equivalent phase shift (EPS) of quarter-wave (λ/4). The EPS is fabricated through extending one sampling period by 50% in the center of a sampled Bragg grating. Single-lobed far-field radiation pattern with a low divergence angle of about 0.6 × 16.8 is obtained. Selective single-mode lasing with a mean side mode suppression ratio above 20 dB and wavelength coverage range of 72 nm is achieved simultaneously on a single wafer only by changing the sampling period. © 2014 AIP Publishing LLC.


Zhang J.,CAS Institute of Semiconductors | Zhang J.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | Liu F.,CAS Institute of Semiconductors | Liu F.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | And 10 more authors.
IEEE Photonics Technology Letters | Year: 2013

We report on the development of λ~4.7 μm continuous-wave (CW) operation of surface grating distributed feedback (DFB) quantum cascade lasers (QCLs). A high wall plug efficiency (WPE) of 7% is obtained at 15 °C from a single facet producing over 0.85 W of CW output power. The threshold current density of DFB QCL is as low as 1.19 kA/cm at 15 °C and 2.29 kA/cm at 90 °C in CW mode. Single-mode operation with side mode suppression ratio above 25 dB is observed in the working temperature of 15 °-95 °C. © 2013 IEEE.


Liu J.,CAS Institute of Semiconductors | Liu J.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | Chen J.,CAS Institute of Semiconductors | Chen J.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | And 12 more authors.
Solid-State Electronics | Year: 2013

Continuous-wave operation of semiconductor terahertz quantum cascade lasers at ∼3.1 THz based on a bound-to-continuum transition design is described. The material physics and device performance is analyzed in detail. With good injection efficiency in the upper single isolated radiative state and efficient extraction from the lower radiative state, the maximum operating temperature is in excess of 90 K in pulsed and 70 K in continuous-wave mode. The peak power of 112.5 mW was obtained at 10 K in pulsed mode, indicating ∼36 photons per injected electron for 120 periods of active region. In continuous-wave operation, collected power of 62 mW and 22 photons per electron was also achieved at 10 K. © 2013 Elsevier Ltd. All rights reserved.


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.


Yan F.-L.,CAS Institute of Semiconductors | Yan F.-L.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | Zhang J.-C.,CAS Institute of Semiconductors | Zhang J.-C.,Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices | And 10 more authors.
Chinese Physics Letters | Year: 2014

We designed and fabricated a six-channel complex-coupled distributed feedback (DFB) quantum cascade laser arrays based on a sampled Bragg grating. The six-channel DFB laser arrays exhibit a linear tuning range of 74 nm centered at a wavelength of 7.55 μm at room temperature. Robust single-mode emission with a side mode suppression ratio about 20 dB was observed, even at full power. The used sampled grating and reflectivity coating on the back facet lead to the peak output power varying from 55 to 82mW with a small difference in slope efficiency from 100 to 128mW/A. © 2014 Chinese Physical Society and IOP Publishing Ltd.

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