Strain engineering plays an important role in improving Ge devices performance, while energy band structure is the theoretical basis for studying the electrical and optical properties of strained Ge. In this paper, the energy band structure of uniaxial strained Ge, over the entire Brillouin zone, is obtained by diagonalizing a 30-band k•p Hamiltonian matrix which includes the spin-orbit coupling interaction and strain effect. According to the band dispersion relation, the conduction band valleys shift and split, as well as electron effective masses, including longitudinal, transverse and density-of-states effective masses are quantitatively evaluated. Calculation results indicate that Ge is converted from an indirect to direct bandgap semiconductor under the [001] and [111] uniaxial tensile stress. The longitudinal and transverse effective masses of L and Δ valleys are not obviously dependent on the uniaxial stress. However, the density-of-states effective masses of L and Δ valleys can be minimized by the [111] and [001] uniaxial compressive stress respectively, which is of benefit to increase the mobility by reducing the probability of electron scattering. These results can provide a theoretical reference for the design of high-performance uniaxial strained Ge devices.

Linjia Di;显英 戴;Dongming Miao;Shujing Wu;跃 郝

Xi'an Dianzi Keji Daxue Xuebao/Journal of Xidian University

2018-6-20

Ultra-lightweight resistive switching memory based on protein has been demonstrated. The memory foil is 0.4 mg cm(-2) , which is 320-fold lighter than silicon substrate, 20-fold lighter than office paper and can be sustained by a human hair. Additionally, high resistance OFF/ON ratio of 10(5) , retention time of 10(4) s, and excellent flexibility (bending radius of 800 μm) have been achieved.

Hong Wang;Bowen Zhu;华 王;Xiaohua Ma;跃 郝;Xiaodong Chen

Small

2016-7-1

The NPIRA structure of the VLSI circuit and yield are discussed, the definition of an optimal (s,8) NPIRA's is presented by the class of (s,8) structure analysis of the interstitial redundant array. A lower bound to the optimal (s,8) interstitial redundant array yield is discussed and given.

Tianxu Zhao;跃 郝;Donggang Xu

Pan Tao Ti Hsueh Pao/Chinese Journal of Semiconductors

1999-6

The high temperature annealing effect of DC characteristics of the different enhancement-mode AlGaN/GaN high-electron-mobility transistors (HEMTs) were investigated. The threshold voltage shifted from 0.12 V to 0.57 V and the gate leakage current was reduced one order after the recessed-gate enhancement-mode AlGaN/GaN HEMTs were annealed at 500 °C for 5 min in N₂ atmosphere. The threshold voltage shifted from 0.23 V to -0.69 V and the gate leakage current increased after the F-implantation enhancement-mode AlGaN/GaN HEMTs were annealed at 400 °C for 2 min in N₂ atmosphere. The height of Schottky barrier increased in annealing process that enhanced the depletion of gate to channel electrons, so that the threshold voltage shifted in the positive direction of x axis, the gate leakage current was reduced and the device can work at higher gate voltage. The depletion of F ions and the increased barrier height of F ions were weakened after annealing, so that the threshold voltage shifted in negative direction of x axis and the gate leakage current increased. The channel electron mobility of F-implantation enhancement-mode AlGaN/GaN HEMTs increased obviously after annealing process.

Chong Wang;Si Quan;Xiao Hua Ma;跃 郝;进成 张;Wei Mao

Wuli Xuebao/Acta Physica Sinica

2010-10

The transport mechanism of reverse surface leakage current in the AlGaN/GaN high-electron mobility transistor (HEMT) becomes one of the most important reliability issues with the downscaling of feature size. In this paper, the research results show that the reverse surface leakage current in AlGaN/GaN HEMT with SiN passivation increases with the enhancement of temperature in the range from 298K to 423K. Three possible transport mechanisms are proposed and examined to explain the generation of reverse surface leakage current. By comparing the experimental data with the numerical transport models, it is found that neither Fowler-Nordheim tunneling nor Frenkel-Poole emission can describe the transport of reverse surface leakage current. However, good agreement is found between the experimental data and the two-dimensional variable range hopping (2D-VRH) model. Therefore, it is concluded that the reverse surface leakage current is dominated by the electron hopping through the surface states at the barrier layer. Moreover, the activation energy of surface leakage current is extracted, which is around 0.083eV. Finally, the SiN passivated HEMT with a high Al composition and a thin AlGaN barrier layer is also studied. It is observed that 2D-VRH still dominates the reverse surface leakage current and the activation energy is around 0.10eV, which demonstrates that the alteration of the AlGaN barrier layer does not affect the transport mechanism of reverse surface leakage current in this paper.

Xue Feng Zheng;Shuang Fan;Yong He Chen;Di Kang;Jian Kun Zhang;Chong Wang;Jiang Hui Mo;Liang Li;Xiao Hua Ma;进成 张;跃 郝

Chinese Physics B

2015-2

We demonstrate an enhancement-mode (E-mode) Al₂O ₃/InAlN/AlN/GaN metal-insulator-semiconductor high-electron-mobility transistor (MISHEMT) with enhanced breakdown voltage. The threshold voltage V_th shifts from %7.6 to 1.8V using fluoride-based plasma treatment. The gate leakage current and the buffer leakage current were reduced by the conduction band modulation of negative fluorine charges. The reduction in the buffer leakage current enhanced the breakdown voltage from 80 to 183V with L_GD = 3 μm. The fabricated E-mode MISHEMT with a gate length of 1 μm exhibits a respectable drain current of 416mA/mm and a peak transconductance of 150mS/mm.

Sheng Lei Zhao;Jun Shuai Xue;Peng Zhang;Bin Hou;Jun Luo;Xiao Jiao Fan;进成 张;Xiao Hua Ma;跃 郝

Applied Physics Express

2014-7

Indium-tin-oxide (ITO) free inverted organic solar cells (IOSCs) based on aluminum-doped zinc oxide (AZO) cathode, low-temperature aqueous solution processed zinc oxide (ZnO) electron extraction layer, and poly(3-hexylthiophene- 2, 5-diyl):[6, 6]-phenyl C₆₁ butyric acid methyl ester blend were realized in this work. The resulted IOSC with ZnO annealed at 150 °C shows the superior power conversion efficiency (PCE) of 3.01%, if decreasing the ZnO annealing temperature to 100 °C, the obtained IOSC also shows a PCE of 2.76%, and no light soaking issue is observed. It is found that this ZnO film not only acts as an effective buffer layer but also slightly improves the optical transmittance of AZO substrates. Further, despite the relatively inferior air-stability, these un-encapsulated AZO/ZnO IOSCs show comparable PCEs to the referenced ITO/ZnO IOSCs, which demonstrates that the AZO cathode is a potential alternative to ITO in IOSCs. Meanwhile, this simple ZnO process is compatible with large area deposition and plastic substrates, and is promising to be widely used in IOSCs and other relative fields.

Dazheng Chen;Chunfu Zhang;Zhizhe Wang;进成 张;Shi Tang;Wei Wei;Li Sun;跃 郝

Applied Physics Letters

2014-6-16

Germanium (Ge) negative capacitance field-effect transistors (NCFETs) with various Zr compositions in Hf_1−xZr_xO₂ (x = 0.33, 0.48, and 0.67) are fabricated and characterized. For each Zr composition, the NCFET exhibits the sudden drop in some points of subthreshold swing (SS), which is induced by the NC effect. Drive current I_DS increases with the increase of annealing temperature, which should be due to the reduced source/drain resistance and improved carrier mobility. The steep SS points are repeatable and stable through multiple DC sweeping measurement proving that they are induced by the NC effect. The values of gate voltage V_GS corresponding to steep SS are consistent and clockwise I_DS-V_GS are maintained through the multiple DC sweeps. At fixed annealing temperature, NC device with Hf_0.52Zr_0.48O₂ achieves the higher I_DS but larger hysteresis compared to the other compositions. NCFET with Hf_0.67Zr_0.33O₂ can obtain the excellent performance with hysteresis-free curves and high I_DS.

Yue Peng;Yan Liu;根全 韩;进成 张;跃 郝

Nanoscale Research Letters

2019

In this paper the trapping effects in Al₂O₃/In_0.17Al_0.83N/GaN MOS-HEMT (here, HEMT stands for high electron mobility transistor) are investigated by frequency-dependent capacitance and conductance analysis. The trap states are found at both the Al₂O₃/InAlN and InAlN/GaN interface. Trap states in InAlN/GaN heterostructure are determined to have mixed de-trapping mechanisms, emission, and tunneling. Part of the electrons captured in the trap states are likely to tunnel into the two-dimensional electron gas (2DEG) channel under serious band bending and stronger electric field peak caused by high Al content in the InAlN barrier, which explains the opposite voltage dependence of time constant and relation between the time constant and energy of the trap states.

Peng Zhang;Sheng Lei Zhao;Jun Shuai Xue;Jie Jie Zhu;Xiao Hua Ma;进成 张;跃 郝

Chinese Physics B

2015-10-20

Hot-carrier effects under AC (Alternating Current) stress are investigated. Alternative hot-hole and hot-electron injection effects on the degradation of NMOSFET's under pulse stress are discussed mainly. Enhanced degradation appears in both threshold voltage and transconductance under pulse stress. NMOSFET's after hot-hole injection followed by hot-electron injection produce serious degradation, which can be explained by neutral-electron-trap model and hot-carrier-induced gate oxide degradation under pulse stress. The pulsed delay time and pulse frequency effects on NMOSFET's degradation are investigated and analyzed quantitatively, and a detailed explanation is also given out. Under pulse stress, the hot-carrier-induced device degradation is caused by the cooperation of hot holes at low voltage and hot electrons at high voltage.

红侠 刘;跃 郝

Tien Tzu Hsueh Pao/Acta Electronica Sinica

2002-5