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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. Source


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. Source


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. Source


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. Source


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. Source

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