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1.
We present first principles calculations of Mn-doped GaN/AlN(0001) heterostructures obtained within the framework of density functional theory by using plane wave pseudopotential techniques. We found that for diluted Mn concentration this system present an integer magnetization that is a fingerprint of half-metallic property; this suggests the possibility to use this junction as a spin injector. 相似文献
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Investigation on threshold voltage of p-channel GaN MOSFETs based on p-GaN/AlGaN/GaN heterostructure 下载免费PDF全文
Ruo-Han Li 《中国物理 B》2021,30(8):87305-087305
The threshold voltage (Vth) of the p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) is investigated via Silvaco-Atlas simulations. The main factors which influence the threshold voltage of p-channel GaN MOSFETs are barrier height Φ1,p, polarization charge density σb, and equivalent unite capacitance Coc. It is found that the thinner thickness of p-GaN layer and oxide layer will acquire the more negative threshold voltage Vth, and threshold voltage |Vth| increases with the reduction in p-GaN doping concentration and the work-function of gate metal. Meanwhile, the increase in gate dielectric relative permittivity may cause the increase in threshold voltage |Vth|. Additionally, the parameter influencing output current most is the p-GaN doping concentration, and the maximum current density is 9.5 mA/mm with p-type doping concentration of 9.5×1016 cm-3 at VGS = -12 V and VDS = -10 V. 相似文献
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针对传统单结GaN基高电子迁移率晶体管器件性能受电流崩塌效应和自加热效应限制的困境,对新型A1GaN/GaN/InGaN/GaN双异质结高电子迁移率晶体管的直流性质展开了系统研究.采用基于热电子效应和自加热效应的流体动力模型,研究了器件在不同偏压下电流崩塌和负微分电导效应与GaN沟道层厚度的相关.研究发现具有高势垒双异质的沟道层能更好地将电子限制在沟道中,显著减小高电场下热电子从沟道层向GaN缓冲层的穿透能力.提高GaN沟道层厚度可以有效抑制电流崩塌和和负微分输出电导,进而提高器件在高场作用下的性能.所得结果为进一步优化双异质结高电子迁移率晶体管结构提供了新思路,可促进新型GaN高电子迁移率晶体管器件在高功率、高频和高温等无线通讯领域内的广泛应用. 相似文献
4.
Improved carrier injection and confinement in InGaN light-emitting diodes containing GaN/AlGaN/GaN triangular barriers 下载免费PDF全文
In this study, an InGaN lighting-emitting diode(LED) containing GaN/AlGaN/GaN triangular barriers is proposed and investigated numerically. The simulation results of output performance, carrier concentration, and radiative recombination rate indicate that the proposed LED has a higher output power and an internal quantum efficiency, and a lower efficiency droop than the LED containing conventional GaN or AlGaN barriers. These improvements mainly arise from the modified energy bands, which is evidenced by analyzing the LED energy band diagram and electrostatic field near the active region.The modified energy bands effectively improve carrier injection and confinement, which significantly reduces electron leakage and increases the rate of radiative recombination in the quantum wells. 相似文献
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High electronic density is achieved by polarization doping without an impurity dopant in graded AIGaN films. Low specific contact resistance is studied on the polarization-doped A1GaN/GaN heterojunctions by using the transmission line method (TLM). The sheet density of polarization-doped A1GaN/GaN heterojunction is 6 × 10 14 cm-2 at room temperature. The linearly graded material structure is demonstrated by X-ray diffraction. The cartier concentration and mobility are characterized by a temperature-dependent Hall measurement. Multiple-layer metal (Ti/A1/Ti/Au) is deposited and annealed at 650 ℃ to realize the Ohmic contacts on the graded A1GaN/GaN heterojunctions. 相似文献
7.
High electronic density is achieved by polarization doping without an impurity dopant in graded AlGaN films. Low specific contact resistance is studied on the polarization-doped AlGaN/GaN heterojunctions by using the transmission line method(TLM). The sheet density of polarization-doped AlGaN/GaN heterojunction is 6×1014cm-2at room temperature.The linearly graded material structure is demonstrated by X-ray diffraction. The carrier concentration and mobility are characterized by a temperature-dependent Hall measurement. Multiple-layer metal(Ti/Al/Ti/Au) is deposited and annealed at 650°C to realize the Ohmic contacts on the graded AlGaN/GaN heterojunctions. 相似文献
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A.C. Mofor F. Reuss A. El-Shaer R. Kling E. Schlenker A. Bakin H. Ahlers U. Siegner S. Sievers M. Albrecht W. Schoch W. Limmer J. Eisenmenger T. Mueller A. Huebel G. Denninger P. Ziemann A. Waag 《Applied Physics A: Materials Science & Processing》2007,88(1):161-166
Doping ZnO with transition metals (TM) is an obvious approach to produce diluted magnetic semiconductors for magnetoelectronic
and spintronic applications. We have carried out experimental studies on the fabrication and characterisation of Mn-doped
ZnO layers and V-doped ZnO layers and nanorods, the results of which are reviewed in this paper. From SQUID measurements,
both epitaxial and implanted ZnMnO layers show paramagnetic behaviour. Epitaxial ZnVO layers show ferromagnetic SQUID signals,
but the presence of any secondary phases in the ZnVO layers may not be ruled out. We also show that the used Al2O3 substrates produce a ferromagnetic SQUID signal, that complicates the analysis of magnetisation data and hence the confirmation
of ferromagnetism only from SQUID results.
PACS 75.50.Pp; 85.75.-d; 81.05.Dz; 75.30.-m; 75.60.Nt; 75.70.-i 相似文献
9.
Rectification and electroluminescence of nanostructured GaN/Si heterojunction based on silicon nanoporous pillar array 下载免费PDF全文
《中国物理 B》2015,(10)
A GaN/Si nanoheterojunction is prepared through growing Ga N nanocrystallites(nc-GaN) on a silicon nanoporous pillar array(Si-NPA) by a chemical vapor deposition(CVD) technique at a relatively low temperature. The average size of nc-Ga N is determined to be ~10 nm. The spectral measurements disclose that the photoluminescence(PL) from GaN/SiNPA is composed of an ultraviolet(UV) band and a broad band spanned from UV to red region, with the feature that the latter band is similar to that of electroluminescence(EL). The electron transition from the energy levels of conduction band and, or, shallow donors to that of deep acceptors of Ga N is indicated to be responsible for both the broad-band PL and the EL luminescence. A study of the I–V characteristic shows that at a low forward bias, the current across the heterojunction is contact-limited while at a high forward bias it is bulk-limited, which follows the thermionic emission model and space-charge-limited current(SCLC) model, respectively. The bandgap offset analysis indicates that the carrier transport is dominated by electron injection from n-GaN into the p-Si-NPA, and the EL starts to appear only when holes begin to be injected from Si-NPA into GaN with biases higher than a threshold voltage. 相似文献
10.
The structural study of diluted magnetic semiconductors is important for interpreting the ferromagnetic behavior associated with the materials. In the present work, a series of low concentration Mn-doped ZnO thin films synthesized by pulsed laser deposition was studied by electron microscopy. All films show the wurtzite structure with (001) preferred growth orientation on the Si substrate. Electron diffraction experiments indicate the deterioration of the growth orientation in some areas of the films with increasing Mn concentration, and the existence of a secondary phase, of Mn2O3-type, in the films with larger Mn concentrations. High-resolution electron microscopy images confirm the existence of the secondary phase in the grain boundary of the Mn-doped ZnO phase. The magnetic properties of Mn-doped ZnO are discussed in relation to the structures of the films. 相似文献
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This paper reports that a large amount of Mn-doped ZnO nanorods have been synthesized through thermal evaporation. The morphologies and properties are studied with x-ray diffraction, a scanning electron microscope, transmission electron microscope and Raman spectroscope. The results indicate that the manganese atoms occupy the zinc vacancies in the wurtzite lattice of ZnO without forming secondary phases. The exact manganese content has been studied by the x-ray fluorescence spectrum. Meanwhile, the magnetic moment versus temperature result proves that the as-prepared Mn-doped ZnO nanorods show ferromagnetic properties at temperatures as high as 400 K. These studies provide a good understanding of the origin of magnetic properties in diluted magnetic semiconductors. 相似文献
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High-performance artificial neurons based on Ag/MXene/GST/Pt threshold switching memristors 下载免费PDF全文
Xiao-Juan Lian 《中国物理 B》2023,32(1):17304-017304
Threshold switching (TS) memristors can be used as artificial neurons in neuromorphic systems due to their continuous conductance modulation, scalable and energy-efficient properties. In this paper, we propose a low power artificial neuron based on the Ag/MXene/GST/Pt device with excellent TS characteristics, including a low set voltage (0.38 V) and current (200 nA), an extremely steep slope (< 0.1 mV/dec), and a relatively large off/on ratio (> 103). Besides, the characteristics of integrate and fire neurons that are indispensable for spiking neural networks have been experimentally demonstrated. Finally, its memristive mechanism is interpreted through the first-principles calculation depending on the electrochemical metallization effect. 相似文献
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LI Na ZHAO Degang & YANG Hui State Key Laboratory on Integrated Optoelectronics Institute of Semiconductors Chinese Academy of Sciences Beijing China 《中国科学G辑(英文版)》2004,47(6):694-701
Because of their large band-gap, large high-field electron velocity, large breakdownfield, and large thermal conductivity, GaN and its heterojunction with AlGaN and InGaNhave foreseeable potential in the applications of high-power/temperature electronics, andoptoelectronic devices operative in UV and visible wavelength. Polarization inducedelectric field can reach the magnitude of ~MV/cm[1,2]. For AlGaN/GaN based FETs theconcentration of sheet carrier induced by polarization in the cha… 相似文献
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利用直流反应溅射方法在p型Si衬底上生长掺Al的n型ZnO薄膜,测量了由n型ZnO薄膜和p型Si衬底组成的异质结在黑暗和光照条件下的I-V特性,结果表明该异质结具有优良的整流特性,而且在光照条件下的反向电流迅速增大并很快趋于饱和.通过测量ZnO薄膜的光电流和异质结的光电压的光谱响应,初步分析了异质结的光电转换机理.测量结果显示,在入射光波长为380nm时光电流强度明显下降,反映出光电流与ZnO薄膜禁带宽度的密切关系;同时还发现,在与ZnO禁带宽度相对应的波长前后所产生的光生电压方向相反.推测这一现象与异质结的能带结构密切相关.
关键词:
ZnO薄膜
异质结
光电转换
光谱响应 相似文献
15.
Enhanced charge carrier injection in heterojunction organic field-effect transistor by inserting an MoO3 buffer layer 下载免费PDF全文
A top-contact organic field-effect transistor(OFET) is fabricated by adopting a pentacene/1,1’-bis(di-4tolylaminophenyl) cyclohexane(TAPC) heterojunction structure and inserting an MoO3 buffer layer between the TAPC organic semiconductor layer and the source/drain electrode.The performances of the heterojunction OFET,including output current,field-effect mobility,and threshed voltage,are all significantly improved by introducing the MoO3 thin buffer layer.The performance improvement of the modified heterojunction OFET is attributed to a better contact formed at the Au/TAPC interface due to the MoO3 thin buffer layer,thereby leading to a remarkable reduction of the contact resistance at the metal/organic interface. 相似文献
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制备了晶格匹配In_(0.17)Al_(0.83)N/GaN异质结圆形平面结构肖特基二极管,通过测试和拟合器件的电容-频率曲线,研究了电容的频率散射机制.结果表明:在频率高于200 kHz后,积累区电容随频率出现增加现象,而传统的电容模型无法解释该现象.通过考虑漏电流、界面态和串联电阻等影响对传统模型进行修正,修正后的电容频率散射模型与实验结果很好地符合,表明晶格匹配In_(0.17)Al_(0.83)N/GaN异质结电容随频率散射是漏电流、界面态和串联电阻共同作用的结果. 相似文献
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K. Shi X.L. Liu D.B. Li J. WangH.P. Song X.Q. XuH.Y. Wei C.M. JiaoS.Y. Yang H. SongQ.S. Zhu Z.G. Wang 《Applied Surface Science》2011,257(18):8110-8112
XPS was used to measure the energy discontinuity in the GaN/diamond heterostructure. The valence band offset (VBO) was determined to be 0.38 ± 0.15 eV and a type-II heterojunction with a conduction band offset (CBO) of 2.43 ± 0.15 eV was obtained. 相似文献
20.
According to first-principles density functional calculations,we have investigated the magnetic properties of Mn-doped GaN with defects,Ga 1-x-y V Gx Mn y N 1-z-t V Nz O t with Mn substituted at Ga sites,nitrogen vacancies V N,gallium vacancies V G and oxygen substituted at nitrogen sites.The magnetic interaction in Mn-doped GaN favours the ferromagnetic coupling via the double exchange mechanism.The ground state is found to be well described by a model based on a Mn 3+-d 5 in a high spin state coupled via a double exchange to a partially delocalized hole accommodated in the 2p states of neighbouring nitrogen ions.The effect of defects on ferromagnetic coupling is investigated.It is found that in the presence of donor defects,such as oxygen substituted at nitrogen sites,nitrogen vacancy antiferromagnetic interactions appear,while in the case of Ga vacancies,the interactions remain ferromagnetic;in the case of acceptor defects like Mg and Zn codoping,ferromagnetism is stabilized.The formation energies of these defects are computed.Furthermore,the half-metallic behaviours appear in some studied compounds. 相似文献