Key Laboratory of Wide Band Gap Semiconductor Materials and Devices

Xi’an, China

Key Laboratory of Wide Band Gap Semiconductor Materials and Devices

Xi’an, China

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Wang C.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | Chen C.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | He Y.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | Zheng X.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | And 4 more authors.
Journal of Semiconductors | Year: 2014

The breakdown and the current collapse characteristics of high electron mobility transistors (HEMTs) with a low power F-plasma treatment process are investigated. With the increase of F-plasma treatment time, the saturation current decreases, and the threshold voltage shifts to the positive slightly. Through analysis of the Schottky characteristics of the devices with different F-plasma treatment times, it was found that an optimal F-plasma treatment time of 120 s obviously reduced the gate reverse leakage current and improved the breakdown voltage of the devices, but longer F-plasma treatment time than 120 s did not reduce gate reverse leakage current due to plasma damage. The current collapse characteristics of the HEMTs with F-plasma treatment were evaluated by dual pulse measurement at different bias voltages and no obvious deterioration of current collapse were found after low power F-plasma treatment. © 2014 Chinese Institute of Electronics.


Zhang W.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | Li X.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | Zhang J.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | Jiang H.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | And 6 more authors.
Physica Status Solidi (A) Applications and Materials Science | Year: 2016

We report Al0.30Ga0.70N/GaN/Al0.07Ga0.93N double-heterostructure high electron mobility transistors (DH HEMTs) with admirable DC characteristics fully surpassing those of the Al0.30Ga0.70N/GaN single-heterostructure (SH) HEMTs. The DH HEMTs feature a 1400-nm graded AlxGa1-xN (x=0-0.06) buffer layer, a 300-nm Al0.07Ga0.93N back barrier layer, and a 70-nm thick GaN channel layer. Due to the improved cystal quality and enhanced confinement of the carriers, the DH HEMTs presented have shown improved performance with respect to the conventional SH HEMTs, including electron mobility promoted from 1701 to 1744cm2V-1s-1, surface roughness in terms of root mean square values (RMS) reduced from 0.19 to 0.16nm, (10-12) full widths at half-maximum (FWHMs) reduced from 726 to 540arcsec, subthreshold swing (SS) reduced from 113 to 78mVdec-1, Ion/Ioff ratio increased from 105.3 to 106.2, drain-induced barrier lowering (DIBL) reduced from 24 and 14mVV-1, and breakdown voltage promoted from 59 to 109V. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Liu L.-X.,Xidian University | Liu L.-X.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | Mu J.-C.,Xidian University | Ma N.,Xidian University | And 5 more authors.
Circuits, Systems, and Signal Processing | Year: 2016

In recent years, radio frequency (RF) energy harvesting systems have gained significant interest as inexhaustible replacements for traditional batteries in RF identification and wireless sensor network nodes. This paper presents an ultra-low-power integrated RF energy harvesting circuit in a SMIC 65-nm standard CMOS process. The presented circuit mainly consists of an impedance-matching network, a 10-stage rectifier with order-2 threshold compensation and an ultra-low-power power manager unit (PMU). The PMU consists of a voltage sensor, a voltage limiter and a capacitor-less low-dropout regulator. In the charge mode, the power consumption of the proposed energy harvesting circuit is only 97 nA, and the RF input power can be as low as (Formula presented.). In the burst mode, the device can supply a 1.0-V DC output voltage with a maximum 10-mA load current. The simulated results demonstrate that the modified RF rectifier can obtain a maximum efficiency of 12 % with a 915-MHz RF input. The circuit can operate over a temperature range from (Formula presented.) which exceeds the achievable temperature performance of previous RF energy harvesters in standard CMOS process. © 2015, Springer Science+Business Media New York.


Liu L.,Xidian University | Liu L.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | Yang Y.-T.,Xidian University | Yang Y.-T.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | Ma X.-H.,Xidian University
Chinese Physics B | Year: 2011

A 4H - silicon carbide metal - insulator - semiconductor structure with ultra-thin Al 2O 3 as the gate dielectric, deposited by atomic layer deposition on the epitaxial layer of a 4H - SiC (0001) 8 0N-/N+ substrate, has been fabricated. The experimental results indicate that the prepared ultra-thin Al 2O 3 gate dielectric exhibits good physical and electrical characteristics, including a high breakdown electrical field of 25 MV/cm, excellent interface properties (1×10 14 cm -2) and low gate-leakage current (I G = 1 × 10 -3 A/cm -2@E ox = 8 MV/cm). Analysis of the current conduction mechanism on the deposited Al 2O 3 gate dielectric was also systematically performed. The confirmed conduction mechanisms consisted of Fowler - Nordheim (FN) tunneling, the Frenkel - Poole mechanism, direct tunneling and Schottky emission, and the dominant current conduction mechanism depends on the applied electrical field. When the gate leakage current mechanism is dominated by FN tunneling, the barrier height of SiC/Al 2O 3 is 1.4 eV, which can meet the requirements of silicon carbide metal - insulator - semiconductor transistor devices. © 2011 Chinese Physical Society and IOP Publishing Ltd.


Ma X.-H.,Xidian University | Cao Y.-R.,Xidian University | Hao Y.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | Zhang Y.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices
Chinese Physics B | Year: 2011

In this paper, we have studied hot carrier injection (HCI) under alternant stress. Under different stress modes, different degradations are obtained from the experiment results. The different alternate stresses can reduce or enhance the HC effect, which mainly depends on the latter condition of the stress cycle. In the stress mode A (DC stress with electron injection), the degradation keeps increasing. In the stress modes B (DC stress and then stress with the smallest gate injection) and C (DC stress and then stress with hole injection under Vg = 0 V and Vd = 1.8 V), recovery appears in the second stress period. And in the stress mode D (DC stress and then stress with hole injection under Vg = -1.8 V and Vd = 1.8 V), as the traps filled in by holes can be smaller or greater than the generated interface states, the continued degradation or recovery in different stress periods can be obtained. © 2011 Chinese Physical Society and IOP Publishing Ltd.


Zhang Y.,Xidian University | Zhang Y.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | Zhou X.,Xidian University | Zhou X.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | And 10 more authors.
AIP Advances | Year: 2015

Pulsed metal organic chemical vapor deposition (P-MOCVD) is introduced into the growth of high quality InGaN channel heterostructures. The effects of InGaN channel growth temperature on the structural and transport properties of the heterostructures are investigated in detail. High resolution x-ray diffraction (HRXRD) and Photoluminescence (PL) spectra indicate that the quality of InGaN channel strongly depends on the growth temperature. Meanwhile, the atomic force microscopy (AFM) results show that the interface morphology between the InGaN channel and the barrier layer also relies on the growth temperature. Since the variation of material properties of InGaN channel has a significant influence on the electrical properties of InAlN/InGaN heterostructures, the optimal transport properties can be achieved by adjusting the growth temperature. A very high two dimension electron gas (2DEG) density of 1.92 × 1013 cm-2 and Hall electron mobility of 1025 cm2/(V·s) at room temperature are obtained at the optimal growth temperature around 740 °C. The excellent transport properties in our work indicate that the heterostructure with InGaN channel is a promising candidate for the microwave power devices, and the results in this paper will be instructive for further study of the InGaN channel heterostructures. © 2015 Author(s).


Niu Y.,Xidian University | Niu Y.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | Zou J.,Xidian University | Zhu Z.,Xidian University | Zhu Z.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices
IEICE Electronics Express | Year: 2013

It is very important for a light source that the brightness could be adjusted conveniently. A novel DC and PWM dual-mode dimming circuit for a monolithic WLED driver is proposed for the first time in this paper. It can alter flexibly the control mode between the analog (DC) and digital (PWM) dimming according to the input control signal. In the DC dimming mode, when the input DC control voltage is adjusted from 0.5 V to 2.5 V, the average output current can be changed from 20% to 100% of the nominal current value. While in the PWM dimming mode, the output current is proportional to the duty cycle of the input PWM signal and changed from about 0% to 100% of the nominal current value. The WLED driver with the proposed dual-mode dimming circuit has been verified in a 0.5 μm HVCMOS process, and the nominal value could be set more than 1 A by the external resistors. © IEICE 2013.


Xue J.S.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | Hao Y.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | Zhang J.C.,Xidian University | Yang L.A.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2010

The effect of growth temperature of AlN interlayers on the properties of GaN epilayers grown on c-plane sapphire by metal organic chemical vapor deposition has been investigated by high resolution X-ray diffraction (HRXRD) and Raman spectroscopy. It is concluded that the crystalline quality of GaN epilayers is improved significantly by using the high temperature AlN (HT-AlN) interlayer in GaN buffers. The density of threading dislocation is reduced especially for edge type dislocations. Higher compressive stress exists in GaN epilayers with HT-AlN interlayer than with low temperature AlN (LT-AlN) interlayer, which is related to the reduction of strain relaxation caused by the formation of misfit dislocation. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Ma X.-H.,Xidian University | Cao Y.-R.,Xidian University | Hao Y.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices
Chinese Physics B | Year: 2010

This paper studies negative bias temperature instability (NBTI) under alternant and alternating current (AC) stress. Under alternant stress, the degradation smaller than that of single negative stress is obtained. The smaller degradation is resulted from the recovery of positive stress. There are two reasons for the recovery. One is the passivation of H dangling bonds, and another is the detrapping of charges trapped in the oxide. Under different frequencies of AC stress, the parameters all show regular degradation, and also smaller than that of the direct current stress. The higher the frequency is, the smaller the degradation becomes. As the negative stress time is too small under higher frequency, the deeper defects are hard to be filled in. Therefore, the detrapping of oxide charges is easy to occur under positive bias and the degradation is smaller with higher frequency. © 2010 Chinese Physical Society and IOP Publishing Ltd.


Duan B.-X.,Xidian University | Duan B.-X.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices | Yang Y.-T.,Xidian University | Yang Y.-T.,Key Laboratory of Wide Band Gap Semiconductor Materials and Devices
Chinese Physics B | Year: 2012

In this paper, two-dimensional electron gas (2DEG) regions in AlGaN/GaN high electron mobility transistors (HEMTs) are realized by doping partial silicon into the AlGaN layer for the first time. A new electric field peak is introduced along the interface between the AlGaN and GaN buffer by the electric field modulation effect due to partial silicon positive charge. The high electric field near the gate for the complete silicon doping structure is effectively decreased, which makes the surface electric field uniform. The high electric field peak near the drain results from the potential difference between the surface and the depletion regions. Simulated breakdown curves that are the same as the test results are obtained for the first time by introducing an acceptor-like trap into the N-type GaN buffer. The proposed structure with partial silicon doping is better than the structure with complete silicon doping and conventional structures with the electric field plate near the drain. The breakdown voltage is improved from 296 V for the conventional structure to 400 V for the proposed one resulting from the uniform surface electric field. © 2012 Chinese Physical Society and IOP Publishing Ltd.

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