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GaN/AlGaN dual-band infrared detection and photon frequency upconversion

Zhou Li-Gang,Shen Wen-Zhong,

物理学报 , 2009,
Abstract: 研究了GaN/AlGaN异质结构中的双带(中、远)红外探测及光子频率上转换特性.通过光致发光光谱确认GaN/AlGaN探测器结构中AlGaN本征层的Al组分,讨论了不同Al组分GaN/AlGaN异质结的导带带阶界面功函数差.在拟合单周期GaN/AlGaN探测器中红外和远红外波段响应谱的基础上,研究多周期GaN/AlGaN探测器与GaN/AlGaN发光二极管集成结构的中红外和远红外光子频率上转换效率与GaN发射层厚度、AlGaN本征层厚度、紫光光子出射效率、内量子效率、空间频率和发射层掺杂浓度间的关系,优化
Unipolar Vertical Transport in GaN/AlGaN/GaN Heterostructures  [PDF]
D. N. Nath,P. S. Park,Z. C. Yang,S. Rajan
Physics , 2013, DOI: 10.1063/1.4813309
Abstract: In this letter, we report on unipolar vertical transport characteristics in c-plane GaN/AlGaN/GaN heterostructures. Vertical current in heterostructures with random alloy barriers was found to be independent of dislocation density and heterostructure barrier height, and significantly higher than theoretical estimates. Percolation-based transport due to random alloy fluctuations in the ternary AlGaN is suggested as the dominant transport mechanism, and confirmed through experiments showing that non-random or digital AlGaN alloys and polarization-engineered binary GaN barriers can eliminate percolation transport and reduce leakage significantly. The understanding of vertical transport and methods for effective control proposed here will greatly impact III-nitride unipolar vertical devices.
Growth and Annealing Study of Mg-Doped AlGaN and GaN/AlGaN Superlattices
WANG Bao-Zhu,WANG Xiao-Liang,HU Guo-Xin,RAN Jun-Xue,WANG Xin-Hua,GUO Lun-Chun,XIAO Hong-Ling,LI Jian-Ping,ZENG Yi-Ping,LI Jin-Min,WANG Zhan-Guo,

中国物理快报 , 2006,
Abstract: Mg-doped AlGaN and GaN/AlGaN superlattices are grown by metalorganic chemical vapour deposition (MOCVD) Rapid thermal annealing (RTA) treatments are carried out on the samples. Hall and high resolution x-ray diffraction measurements are used to characterize the electrical and structural prosperities of the as-grown and annealed samples, respectively. The results of hall measurements show that after annealing, the Mg-doped AIGaN sample can not obtain the distinct hole concentration and can acquire a resistivity of 1.4 ×10^3 Ωcm. However, with the same annealing treatment, the GaN/AlGaN superlattice sample has a hole concentration of 1.7 × 10^17 cm-3 and a resistivity of 5.6Ωcm. The piezoelectric field in the GaN/AlGaN superlattices improves the activation efficiency of Mg acceptors, which leads to higher hole concentration and lower p-type resistivity.
Ultraviolet Phototransistors on AlGaN/GaN Heterostructures
CHEN Chen,JIANG Wen-Hai,REN Chun-Jiang,LI Zhong-Hui,JIAO Gang,DONG Xun,CHEN Tang-Sheng,

中国物理快报 , 2007,
Abstract: We report on the fabrication and characterization of phototransistors based on AlGaN/GaN heterostructure grown over 6H-SiC substrates. The device has two functions: as a high electron mobility transistor (HEMT) and an ultraviolet photodetector at the same time. As an HEMT, its maximum transconductance is 170mS/mm, while the minimum cutoff frequency fT and the maximum oscillation frequency fm are 19 and 35GHz, respectively. As a photodetector, the device is visible blind, with an ultraviolet/green contrast of three orders of magnitude, and a responsivity as high as 1700A/W at the wavelength of 362nm.
Influence of dislocations in the GaN layer on the electrical properties of an AlGaN/GaN heterostructure

Gao Zhi-Yuan,Hao Yue,Zhang Jin-Cheng,Li Pei-Xian,Gu Wen-Ping,

中国物理 B , 2009,
Abstract: This paper reports on a comparative study of the spatial distributions of the electrical, optical, and structural properties in an AlGaN/GaN heterostructure. Edge dislocation density in the GaN template layer is shown to decrease in the regions of the wafer where the heterostructure sheet resistance increases and the GaN photoluminescence band-edge energy peak shifts to a high wavelength. This phenomenon is found to be attributed to the local compressive strain surrounding edge dislocation, which will generate a local piezoelectric polarization field in the GaN layer in the opposite direction to the piezoelectric polarization field in the AlGaN layer and thus help to increase the two-dimensional electron gas concentration.
Numerical Explanation of Slow Transients in an AlGaN/GaN HEMT
Zhang Jinfeng,Hao Yue,
Zhang Jinfeng
,Hao Yue

半导体学报 , 2006,
Abstract: A series of slow drain current recovery transients at different gate biases after a short-term stress are observed in an AlGaN/GaN HEMT.As the variation of the time constants of the transients is small,the working trap is determined to be electronic.A numerical simulation verifies this conclusion and reproduces the measured transients.The electron traps at different spatial positions in the device-on the ungated surface of the AlGaN layer,in the AlGaN barrier,and in the GaN layer are considered;corresponding behaviors in the stress and the transients are discussed;and for the simulated transients,agreement with and deviation from the measured transients are explained.Based on this discussion,we suggest that the measured transients are caused by the combined effects of a deep surface trap and a bulk trap in the GaN layer.
Electron Scattering in AlGaN/GaN Structures  [PDF]
S. Syed,M. J. Manfra,Y. J. Wang,R. J. Molnar,H. L. Stormer
Physics , 2003, DOI: 10.1063/1.1655704
Abstract: We present data on mobility lifetime, $\tau_t$, quantum lifetime, $\tau_q$, and cyclotron resonance lifetime, $\tau_{CR}$, of a sequence of high-mobility two-dimensional electron gases in the AlGaN/GaN system, covering a density range of $\sim1-4.5\times10^{12}$cm$^{-2}$. We observe a large discrepancy between $\tau_q$ and $\tau_{CR}$ ($\tau_q\sim\tau_{CR}$/6) and explain it as the result of density fluctuations of only a few percent. Therefore, only $\tau_{CR}$ --and not $\tau_q$ -- is a reliable measure of the time between electron scattering events in these specimens. The ratio $\tau_t / \tau_{CR}$ increases with increasing density in this series of samples, but scattering over this density range remains predominantly in the large-angle scattering regime.
Effects of the strain relaxation of an AlGaN barrier layer induced by various cap layers on the transport properties in AlGaN/GaN heterostructures

Liu Zi-Yang,Zhang Jin-Cheng,Duan Huan-Tao,Xue Jun-Shuai,Lin Zhi-Yu,Ma Jun-Cai,Xue Xiao-Yong,Hao Yue,

中国物理 B , 2011,
Abstract: The strain relaxation of an AlGaN barrier layer may be influenced by a thin cap layer above, and affects the transport properties of AlGaN/GaN heterostructures. Compared with the slight strain relaxation found in AlGaN barrier layer without cap layer, it is found that a thin cap layer can induce considerable changes of strain state in the AlGaN barrier layer. The degree of relaxation of the AlGaN layer significantly influences the transport properties of the two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures. It is observed that electron mobility decreases with the increasing degree of relaxation of the AlGaN barrier, which is believed to be the main cause of the deterioration of crystalline quality and morphology on the AlGaN/GaN interface. On the other hand, both GaN and AlN cap layers lead to a decrease in 2DEG density. The reduction of 2DEG caused by the GaN cap layer may be attributed to the additional negative polarization charges formed at the interface between GaN and AlGaN, while the reduction of the piezoelectric effect in the AlGaN layer results in the decrease of 2DEG density in the case of AlN cap layer.
Improvement of the efficiency droop of GaN-LEDs using an AlGaN/GaN superlattice insertion layer

Ji Panfeng,Liu Naixin,Wei Tongbo,Liu Zhe,Lu Hongxi,Wang Junxi,Li Jinmin,

半导体学报 , 2011,
Abstract: 在GaN基LED的n-GaN和InGaN/GaN发光区之间插入n-AlGaN/GaN超晶格来改善其droop效应。注入电流低于100mA时,插入n-AlGaN/GaN超晶格的LED的流明效率低于没有插入层的LED。注入电流高于100mA时,插入n-AlGaN/GaN超晶格的LED的流明效率高于没有插入层的LED。插入n-AlGaN/GaN超晶格后,GaN基LED在-5V的反向电压下,漏电由2.568029μA减少到0.070543μA。人体模式下,插入n-AlGaN/GaN超晶格的LED在2000V的静电电压下的通过率从60%提高到了90%。LED droop效应的改善是因为n-AlGaN/GaN超晶格过滤了穿透位错并改善了电流扩展能力。
Design and Implementation of Ka-band AlGaN/GaN HEMTs
Ka波段AlGaN/GaN HEMT的研制

WANG Dong-Fang,YUAN Ting-Ting,WEI Ke,LIU Xin-Yu,LIU Guo-Guo,

红外与毫米波学报 , 2011,
Abstract: 采用缩小源漏间距、优化栅结构和外围结构等措施设计了AlGaN/GaN HEMT,并基于国内的GaN外延片和工艺完成了器件制备。测试表明所研制的AlGaN/GaN HEMT 可以满足Ka波段应用。其中2 75μm栅宽AlGaN/GaN HEMT在30V漏压下的截止频率(ft)为32GHz,最大振荡频率(fmax)为150GHz;在30GHz连续波测试条件下,线性增益达到10.2dB。6 75μm栅宽AlGaN/GaN HEMT的截止频率为32GHz,最大振荡频率为92GHz;在30GHz连续波测试条件下,线性增益达到8.5dB。器件的击穿电压在60V以上。
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