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 共查询到17条相似文献,搜索用时 174 毫秒
1.
林芳  沈波  卢励吾  马楠  许福军  苗振林  宋杰  刘新宇  魏珂  黄俊 《中国物理 B》2010,19(12):127304-127304
In contrast with Au/Ni/Al 0.25 Ga 0.75 N/GaN Schottky contacts,this paper systematically investigates the effect of thermal annealing of Au/Pt/Al 0.25 Ga 0.75 N/GaN structures on electrical properties of the two-dimensional electron gas in Al 0.25 Ga 0.75 N/GaN heterostructures by means of temperature-dependent Hall and temperature-dependent current-voltage measurements.The two-dimensional electron gas density of the samples with Pt cap layer increases after annealing in N 2 ambience at 600℃ while the annealing treatment has little effect on the two-dimensional electron gas mobility in comparison with the samples with Ni cap layer.The experimental results indicate that the Au/Pt/Al 0.25 Ga 0.75 N/GaN Schottky contacts reduce the reverse leakage current density at high annealing temperatures of 400-600℃.As a conclusion,the better thermal stability of the Au/Pt/Al 0.25 Ga 0.75 N/GaN Schottky contacts than the Au/Ni/Al 0.25 Ga 0.75 N/GaN Schottky contacts at high temperatures can be attributed to the inertness of the interface between Pt and AlxGa1-xN.  相似文献   

2.
李菲  张小玲  段毅  谢雪松  吕长志 《中国物理 B》2009,18(11):5029-5033
Fundamentals of the Schottky contacts and the high-temperature current conduction through three kinds of Schottky diodes are studied.N-Si Schottky diodes,GaN Schottky diodes and AlGaN/GaN Schottky diodes are investigated by I–V –T measurements ranging from 300 to 523 K.For these Schottky diodes,a rise in temperature is accompanied with an increase in barrier height and a reduction in ideality factor.Mechanisms are suggested,including thermionic emission,field emission,trap-assisted tunnelling and so on.The most remarkable finding in the present paper is that these three kinds of Schottky diodes are revealed to have different behaviours of high-temperature reverse currents.For the n-Si Schottky diode,a rise in temperature is accompanied by an increase in reverse current.The reverse current of the GaN Schottky diode decreases first and then increases with rising temperature.The AlGaN/GaN Schottky diode has a trend opposite to that of the GaN Schottky diode,and the dominant mechanisms are the effects of the piezoelectric polarization field and variation of two-dimensional electron gas charge density.  相似文献   

3.
刘红侠  吴笑峰  胡仕刚  石立春 《中国物理 B》2010,19(5):57303-057303
Current transport mechanism in Ni-germanide/n-type Ge Schottky diodes is investigated using current-voltage characterisation technique with annealing temperatures from 300 C to 500 C.Based on the current transport model,a simple method to extract parameters of the NiGe/Ge diode is presented by using the I-V characteristics.Parameters of NiGe/n-type Ge Schottky diodes fabricated for testing in this paper are as follows:the ideality factor n,the series resistance Rs,the zero-field barrier height b0,the interface state density Dit,and the interfacial layer capacitance Ci.It is found that the ideality factor n of the diode increases with the increase of annealing temperature.As the temperature increases,the interface defects from the sputtering damage and the penetration of metallic states into the Ge energy gap are passivated,thus improving the junction quality.However,the undesirable crystallisations of Ni-germanide are observed together with NiGe at a temperature higher than 400 C.Depositing a very thin(~1 nm) heavily Ge-doped n+ Ge intermediate layer can improve the NiGe film morphology significantly.  相似文献   

4.
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 298 K to 423 K.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 0.083 eV.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 0.10 eV,which demonstrates that the alteration of the AlGaN barrier layer does not affect the transport mechanism of reverse surface leakage current in this paper.  相似文献   

5.
刘芳  王涛  沈波  黄森  林芳  马楠  许福军  王鹏  姚建铨 《中国物理 B》2009,18(4):1618-1621
Recently GaN-based high electron mobility transistors (HEMTs) have revealed the superior properties of a high breakdown field and high electron saturation velocity. Reduction of the gate leakage current is one of the key issues to be solved for their further improvement. This paper reports that an Al layer as thin as 3 nm was inserted between the conventional Ni/Au Schottky contact and n-GaN epilayers, and the Schottky behaviour of Al/Ni/Au contact was investigated under various annealing conditions by current-voltage (I-V ) measurements. A non-linear fitting method was used to extract the contact parameters from the I-V characteristic curves. Experimental results indicate that reduction of the gate leakage current by as much as four orders of magnitude was successfully recorded by thermal annealing. And high quality Schottky contact with a barrier height of 0.875 eV and the lowest reverse-bias leakage current, respectively, can be obtained under 12 min annealing at 450 C in N2 ambience.  相似文献   

6.
GaSb-based 2.4μm InGaAsSb/AIGaAsSb type-I quantum-well laser diode is fabricated. The laser is designed consisting of three In0.35 Ga0.65As0.1Sb0.9/Al0.35 Ga0.65 As0.02Sb0.98 quantum wells with 1% compressive strain located in the central part of an undoped Al0.35Ga0.65As0.02Sb0.98 waveguide layer. The output power of the laser with a 50-μm-wide i-ram-long cavity is 28roW, and the threshold current density is 400A/cm2 under continuous wave operation mode at room temperature.  相似文献   

7.
Both the peak position and linewidth in the photoluminescence spectrum of the InAs/GaAs quantum dots usually vary in an anomalous way with increasing temperature. Such anomalous optical behaviour is eliminated by inserting an In0.2Ga0.8As quantum well below the quantum dot layer in molecular beam epitaxy. The insensitivity of the photoluminescence spectra to temperature is explained in terms of the effective carrier redistribution between quantum dots through the In0.2Ga0.8As quantum well.  相似文献   

8.
The leakage current of GaN Schottky barrier ultraviolet photodetectors is investigated.It is found that the photodetectors adopting undoped GaN instead of lightly Si-doped GaN as an active layer show a much lower leakage current even when they have a higher dislocation density.It is also found that the density of Ga vacancies in undoped GaN is much lower than in Si-doped GaN.The Ga vacancies may enhance tunneling and reduce effective Schottky barrier height,leading to an increase of leakage current.It suggests that when undoped GaN is used as the active layer,it is necessary to reduce the leakage current of GaN Schottky barrier ultraviolet photodetector.  相似文献   

9.
茹国平  俞融  蒋玉龙  阮刚 《中国物理 B》2010,19(9):97304-097304
This paper investigates the thermal activation behaviour of current in an inhomogeneous Schottky diode with a Gaussian distribution of barrier height by numerical simulation. The analytical Gaussian distribution model predicted that the I-V -T curves may intersect with the possibility of the negative thermal activation of current, but may be contradictory to the thermionic emission mechanism in a Schottky diode. It shows that the cause of the unphysical phenomenon is related to the incorrect calculation of current across very low barriers. It proposes that junction voltage Vj, excluding the voltage drop across series resistance from the external bias, is a crucial parameter for correct calculation of the current across very low barriers. For correctly employing the thermionic emission model, Vj needs to be smaller than the barrier height Ф. With proper scheme of series resistance connection where the condition of Vj >Ф is guaranteed, I-V -T curves of an inhomogeneous Schottky diode with a Gaussian distribution of barrier height have been simulated, which demonstrate normal thermal activation. Although the calculated results exclude the intersecting possibility of I-V -T curves with an assumption of temperature-independent series resistance, it shows that the intersecting is possible when the series resistance has a positive temperature coefficient. Finally, the comparison of our numerical and analytical results indicates that the analytical Gaussian distribution model is valid and accurate in analysing I-V -T curves only for small barrier height inhomogeneity.  相似文献   

10.
The current transport parameters of 4H-SiC merged PiN Schottky(MPS) diode are investigated in a temperature range of 300-520 K.Evaluation of the experimental current-voltage(I-V) data reveals the decrease in Schottky barrier height Φ b but an increase in ideality factor n,with temperature decreasing,which suggests the presence of an inhomogeneous Schottky barrier.The current transport behaviours are analysed in detail using the Tung’s model and the effective area of the low barrier patches is extracted.It is found that small low barrier patches,making only 4.3% of the total contact,may significantly influence the device electrical characteristics due to the fact that a barrier height of 0.968 eV is much lower than the average barrier height 1.39 eV.This shows that ion implantation in the Schottky contact region of MPS structure may result in a poor Ti/4H-SiC interface quality.In addition,the temperature dependence of the specific on-resistance(R on sp),T 2.14,is determined between 300 K and 520 K,which is similar to that predicted by a reduction in electron mobility.  相似文献   

11.
采用60Co γ射线源对高铝组分Al0.5Ga0.5N盲紫外p-i-n结构光探测器和Si基可见光p-i-n结构探测器进行了累计剂量分别为0.1, 1, 10 Mrad(Si)总剂量辐照实验. 实验发现, 随着辐照剂量的增加, AlGaN盲紫外p-i-n结构光探测器的理想因子显著增大, 辐照后理想因子n > 2; 而Si基可见光p-i-n 结构探测器的理想因子随辐照剂量的变化并不明显. AlGaN盲紫外p-i-n结构光探测器理想因子的退化可能主要是因为欧姆接触性能的退化, Si基可见光p-i-n结构探测器的理想因子的变化则可能是由于敏感层的退化. 关键词xGa1?xN')" href="#">高铝组分AlxGa1?xN γ射线辐射效应 理想因子 欧姆接触  相似文献   

12.
Using polarization field effect-based thermionic field emission (PFE-TFE) model based on current–voltage–temperature data, possible carrier transport mechanisms for Pt/Au and Cr/Pd Schottky contacts to Al0.25Ga0.75N/GaN layers were investigated. Thermionic emission (TE) model was also investigated to compare to the PFE-TFE. It was shown that Schottky barrier heights (SBHs) are significantly affected by a polarization field-induced carrier density of the AlGaN layer. In addition, relatively little temperature dependence on the leakage current density of both contacts was found, which is in good agreement with the PFE-TFE model. The results indicate that the TFE is responsible for the current flow across the metal/AlGaN–GaN interface at T ≥ 293 K.  相似文献   

13.
Electrical devices involve different types of diode in prospective electronics is of great importance. In this study, p-type Si surface was covered with thin film of TiO2 dispersion in H2O to construct p-Si/TiO2/Al Schottky barrier diode (D1) and the other one with TiO2 dispersion doped with zirconium to construct p-Si/TiO2-Zr/Al diode (D2) by drop-casting method in the same conditions. Electrical properties of as-prepared diodes and effect of zirconium as a dopant were investigated. Current–voltage (IV) characteristics of these devices were measured at ambient conditions. Some parameters including ideality factor (n), barrier height (ΦB0), series resistance (Rs) and interface state density (Nss) were calculated from IV behaviours of diodes. Structural comparisons were based on SEM and EDX measurements. Experimental results indicated that electrical parameters of p-Si/TiO2/Al Schottky device were influenced by the zirconium dopant in TiO2.  相似文献   

14.
Organic solar cells using the CuPc and PTCBI semiconductor layers were studied. A high open circuit voltage of 1.15 V was obtained in a device with ITO/PEDOT:PSS/CuPc (15 nm)/PTCBI (7 nm)/Al structure. Results were interpreted in terms of a modified CuPc-Al Schottky diode for the thin PTCBI case and a CuPc-PTCBI heterojunction for the thick PTCBI case. Also, the formation of a thin aluminum oxide layer under the aluminum electrode was postulated. This layer has a beneficial aspect wherein shunting losses are reduced and a high photovoltage is enabled. However, it adds greatly to the series resistance to a point where the short circuit current density is reduced. CuPc Schottky diodes with an ITO/PEDOT:PSS/CuPc/Al structure yielded a high V oc of 900 mV for a CuPc layer of thickness 140 nm. The V oc increased with increase in CuPc layer thickness.  相似文献   

15.
We investigated the optical properties and electrical properties of N-doped ZnO layers grown on (0 0 0 1) GaN/Al2O3 substrates by molecular beam epitaxy, employing 10 K photoluminescence (PL) measurements, current–voltage (IV) measurements, capacitance–voltage (CV) measurements, and 100 K photocapacitance (PHCAP) measurements. 10 K PL spectra showed that excitonic emission is dominant in N-doped ZnO layers grown after O-plasma exposure, while overall PL emission intensity is significantly reduced and deep level emission at around 2.0 2.2 eV is dominant in N-doped ZnO layers grown after Zn exposure. IV and CV measurements showed that N-doped ZnO layers grown after Zn exposure have better Schottky diode characteristics than O-plasma exposed samples, and an N-doped ZnO layer grown at 300 °C after Zn exposure has best Schottky diode characteristics. This phenomenon is presumably due to lowered background electron concentration induced by the incorporation of N. PHCAP measurements for the N-doped ZnO layer revealed several midgap trap centers at 1.2 1.8 eV below conduction band minimum.  相似文献   

16.
《Composite Interfaces》2013,20(2):127-135
Al0.11Ga0.89N/GaN samples are grown by plasma-assisted molecular beam epitaxy method on (1 1 1) silicon substrates. High purity gallium (7N) and aluminum (6N5) were used to grow Al0.11Ga0.89N, GaN, and AlN, respectively. The surface morphology, structural and optical properties of the sample has been investigated by scanning electron microscope (SEM), and high-resolution X-ray diffraction (HR-XRD), respectively. HR-XRD measurement showed that the sample has a typical diffraction pattern of hexagonal Al0.11Ga0.89N/GaN heterostructures. Ni/Ag bilayers are deposited on Al0.11Ga0.89N as the Schottky contacts. The effect of annealing in oxygen ambient on the electrical properties of Ni/Ag/Al0.11Ga0.89N is studied by current–voltage measurement. The annealing at a temperature of 700 °C for 10?min results in an increase in the ideality factor from 1.033 to 1.042 and an increase in the Schottky barrier height from 0.708 to 0.811 eV. Furthermore, the annealing in oxygen ambient also leads to an increase in the surface roughness of the contacts from 0.0098 to 0.1360 μm which is in agreement with the SEM results.  相似文献   

17.
The effect of oxygen plasma treatment on the performance of GaN Schottky barrier diodes is studied. The GaN surface is intentionally exposed to oxygen plasma generated in an inductively coupled plasma etching system before Schottky metal deposition. The reverse leakage current of the treated diodes is suppressed in low bias range with enhanced diode ideality factor and series resistance. However, in high bias range the treated diodes exhibit higher reverse leakage current and corresponding lower breakdown voltage. The X-ray photoelectron spectroscopy analysis reveals the growth of a thin GaOx layer on GaN surface during oxygen plasma treatment. Under sub-bandgap light illumination, the plasma-treated diodes show larger photovoltaic response compared with that of untreated diodes, suggesting that additional defect states at GaN surface are induced by the oxygen plasma treatment.  相似文献   

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