共查询到20条相似文献,搜索用时 15 毫秒
1.
An AlGaN/GaN high-electron mobility transistor (HEMT) with a novel source-connected air-bridge field plate (AFP) is experimentally verified. The device features a metal field plate that jumps from the source over the gate region and lands between the gate and drain. When compared to a similar size HEMT device with conventional field plate (CFP) structure, the AFP not only minimizes the parasitic gate to source capacitance, but also exhibits higher OFF-state breakdown voltage and one order of magnitude lower drain leakage current. In a device with a gate to drain distance of 6 μm and a gate length of 0.8 μm, three times higher forward blocking voltage of 375 V was obtained at VGS=-5 V. In contrast, a similar sized HEMT with CFP can only achieve a breakdown voltage no higher than 125 V using this process, regardless of device dimensions. Moreover, a temperature coefficient of 0 V/K for the breakdown voltage is observed. However, devices without field plate (no FP) and with optimized conventional field plate (CFP) exhibit breakdown voltage temperature coefficients of -0.113 V/K and -0.065 V/K, respectively. 相似文献
2.
A reduced surface electric field in an AlGaN/GaN high electron mobility transistor(HEMT) is investigated by employing a localized Mg-doped layer under the two-dimensional electron gas(2-DEG) channel as an electric field shaping layer.The electric field strength around the gate edge is effectively relieved and the surface electric field is distributed evenly as compared with those of HEMTs with conventional source-connected field plate and double field plate structures with the same device physical dimensions.Compared with the HEMTs with conventional sourceconnected field plates and double field plates,the HEMT with a Mg-doped layer also shows that the breakdown location shifts from the surface of the gate edge to the bulk Mg-doped layer edge.By optimizing both the length of Mg-doped layer,L m,and the doping concentration,a 5.5 times and 3 times the reduction in the peak electric field near the drain side gate edge is observed as compared with those of the HEMTs with source-connected field plate structure and double field plate structure,respectively.In a device with V GS = -5 V,L m = 1.5 μm,a peak Mg doping concentration of 8×10 17cm-3 and a drift region length of 10 μm,the breakdown voltage is observed to increase from 560 V in a conventional device without field plate structure to over 900 V without any area overhead penalty. 相似文献
3.
Parvesh Gangwani Ravneet Kaur Sujata Pandey Subhasis Haldar Mridula Gupta R.S. Gupta 《Superlattices and Microstructures》2008
The paper presents an accurate charge control model for a fully strained (FS), and partially relaxed (PR) lattice mismatched AlGaN/GaN HEMT, taking into consideration the effect of spontaneous and piezoelectric polarization. The model also accounts for the mobility degradation with increase in temperature, which is one of the major causes in deterioration of the driving current. By using the variation of band gap with temperature, the temperature dependence on threshold voltage, sheet carrier concentration and drain current is studied. Further, the temperature variation shows the applicability of the device in a variable thermal environment. A close agreement of calculated data with simulated/experimental data proves the validity of the model. 相似文献
4.
Reverse blocking enhancement of drain field plate in Schottky-drain AlGaN/GaN high-electron mobility transistors
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In this paper, we present the combination of drain field plate(FP) and Schottky drain to improve the reverse blocking capability, and investigate the reverse blocking enhancement of drain FP in Schottky-drain AlGaN/GaN high-electron mobility transistors(HEMTs). Drain FP and gate FP were employed in a two-dimensional simulation to improve the reverse blocking voltage(VRB) and the forward blocking voltage(VFB). The drain-FP length, the gate-FP length and the passivation layer thickness were optimized. VRBand VFBwere improved from-67 V and 134 V to-653 V and 868 V respectively after optimization. Simulation results suggest that the combination of drain FP and Schottky drain can enhance the reverse blocking capability significantly. 相似文献
5.
为了缓解AlGaN/GaNhighelectronmobilitytransistors(HEMT)器件n型GaN缓冲层高的泄漏电流,本文提出了具有氟离子注入新型Al0.25Ga0.75N/GaNHEMT器件新结构.首先分析得出n型GaN缓冲层没有受主型陷阱时,器件输出特性为欧姆特性,这样就从理论和仿真方面解释了文献生长GaN缓冲层掺杂Fe,Mg等离子的原因.利用器件输出特性分别分析了栅边缘有和没有低掺杂漏极时,氟离子分别注入源区、栅极区域和漏区的情况,得出当氟离子注入源区时,形成的受主型陷阱能有效俘获源极发射的电子而减小GaN缓冲层的泄漏电流,击穿电压达到262v通过减小GaN缓冲层体泄漏电流,提高器件击穿电压,设计具有一定输出功率新型A1GaN/GaNHEMT提供了科学依据. 相似文献
6.
Mechanism of improving forward and reverse blocking voltages in AlGaN/GaN HEMTs by using Schottky drain
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In this paper, we demonstrate that a Schottky drain can improve the forward and reverse blocking voltages(BVs)simultaneously in AlGaN/GaN high-electron mobility transistors(HEMTs). The mechanism of improving the two BVs is investigated by analysing the leakage current components and by software simulation. The forward BV increases from72 V to 149 V due to the good Schottky contact morphology. During the reverse bias, the buffer leakage in the Ohmicdrain HEMT increases significantly with the increase of the negative drain bias. For the Schottky-drain HEMT, the buffer leakage is suppressed effectively by the formation of the depletion region at the drain terminal. As a result, the reverse BV is enhanced from-5 V to-49 V by using a Schottky drain. Experiments and the simulation indicate that a Schottky drain is desirable for power electronic applications. 相似文献
7.
Improvement of breakdown characteristics of an A1GaN/GaN HEMT with a U-type gate foot for millimeter-wave power application
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<正>In this study,the physics-based device simulation tool Silvaco ATLAS is used to characterize the electrical properties of an AlGaN/GaN high electron mobility transistor(HEMT) with a U-type gate foot.The U-gate AlGaN/GaN HEMT mainly features a gradually changed sidewall angle,which effectively mitigates the electric field in the channel, thus obtaining enhanced off-state breakdown characteristics.At the same time,only a small additional gate capacitance and decreased gate resistance ensure excellent RF characteristics for the U-gate device.U-gate AlGaN/GaN HEMTs are feasible through adjusting the etching conditions of an inductively coupled plasma system,without introducing any extra process steps.The simulation results are confirmed by experimental measurements.These features indicate that U-gate AlGaN/GaN HEMTs might be promising candidates for use in miltimeter-wave power applications. 相似文献
8.
AlGaN/GaN high-electron-mobility transistors (HEMTs) with Al-doped ZnO (AZO) transparent gate electrodes are fabricated, and Ni/Au/Ni-gated HEMTs are produced in comparison. The AZO-gated HEMTs show good DC characteristics and Schottky rectifying characteristics, and the gate electrodes achieve excellent transparencies. Compared with Ni/Au/Ni-gated HEMTs, AZO-gated HEMTs show a low saturation current, high threshold voltage, high Schottky barrier height, and low gate reverse leakage current. Due to the higher gate resistivity, AZO-gated HEMTs exhibit a current-gain cutoff frequency (fT) of 10 GHz and a power gain cutoff frequency (fmax) of 5 GHz, and lower maximum oscillation frequency than Ni/Au/Ni-gated HEMTs. Moreover, the C-V characteristics are measured and the gate interface characteristics of the AZO-gated devices are investigated by a C-V dual sweep. 相似文献
9.
In this paper, a high performance AlGaN/GaN High Electron Mobility Transistor (HEMT) on SiC substrates is presented to improve the electrical operation with the amended depletion region using a multiple recessed gate (MRG–HEMT). The basic idea is to change the gate depletion region and a better distribution of the electric field in the channel and improve the device breakdown voltage. The proposed gate consists of lower and upper gate to control the channel thickness. Also, the charge of the depletion region will change due to the optimized gate. In addition, a metal between the gate and drain including the horizontal and vertical parts is used to better control the thickness of the channel. The breakdown voltage, maximum output power density, cut-off frequency, maximum oscillation frequency, minimum noise figure, maximum available gain (MAG), and maximum stable gain (MSG) are some parameters for designers which are considered and are improved in this paper. 相似文献
10.
Monolithic integration of an AlGaN/GaN metalinsulator field-effect transistor with an ultra-low voltage-drop diode for self-protection
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In this paper,we present a monolithic integration of a self-protected AlGaN/GaN metal-insulator field-effect transistor(MISFET).An integrated field-controlled diode on the drain side of the AlGaN/GaN MISFET features a selfprotected function for a reverse bias.This diode takes advantage of the recessed-barrier enhancement-mode technique to realize an ultra-low voltage drop and a low turn-ON voltage.In the smart monolithic integration,this integrated diode can block a reverse bias(> 70 V/μm) and suppress the leakage current(< 5 × 10-11 A/mm).Compared with conventional monolithic integration,the numerical results show that the MISFET integrated with a field-controlled diode leads to a good performance for smart power integration.And the power loss is lower than 50% in conduction without forward current degeneration. 相似文献
11.
The degradation and recovery properties of AlGaN/GaN high-electron mobility transistors under direct current reverse step voltage stress
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Direct current(DC) reverse step voltage stress is applied on the gate of an AlGaN/GaN high-electron mobility transistor(HEMT).Experiments show that parameters degenerate under stress.Large-signal parasitic source/drain resistance(RS/RD) and gate-source forward I-V characteristics are recoverable after breakdown of the device under test(DUT).Electrons trapped by both the AlGaN barrier trap and the surface state under stress lead to this phenomenon,and surface state recovery is the major reason for the recovery of device parameters. 相似文献
12.
Min-Woo Ha Seung-Chul Lee Soo-Seong Kim Chong-Man Yun Min-Koo Han 《Superlattices and Microstructures》2006,40(4-6):562
A new AlGaN/GaN high electron mobility transistor (HEMT) employing Ni/Au Schottky gate oxidation and benzocyclobutene (BCB) passivation is fabricated in order to increase a breakdown voltage and forward drain current. The Ni/Au Schottky gate metal with a thickness of 50/300 nm is oxidized under oxygen ambient at 500 C and the highly resistive NiO is formed at the gate edge. The leakage current of AlGaN/GaN HEMTs is decreased from 4.94 μA to 3.34 nA due to the formation of NiO. The BCB, which has a low dielectric constant, successfully passivates AlGaN/GaN HEMTs by suppressing electron injection into surface states. The BCB passivation layer has a low capacitance, so BCB passivation increases the switching speed of AlGaN/GaN HEMTs compared with silicon nitride passivation, which has a high dielectric constant. The forward drain current of a BCB-passivated device is 199 mA /mm, while that of an unpassivated device is 172 mA /mm due to the increase in two-dimensional electron gas (2DEG) charge. 相似文献
13.
Breakdown characteristics of AlGaN/GaN Schottky barrier diodes fabricated on a silicon substrate
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In this work, the breakdown characteristics of AlGaN/GaN planar Schottky barrier diodes(SBDs) fabricated on the silicon substrate are investigated. The breakdown voltage(BV) of the SBDs first increases as a function of the anodeto-cathode distance and then tends to saturate at larger inter-electrode spacing. The saturation behavior of the BV is likely caused by the vertical breakdown through the intrinsic GaN buffer layer on silicon, which is supported by the postbreakdown primary leakage path analysis with the emission microscopy. Surface passivation and field plate termination are found effective to suppress the leakage current and enhance the BV of the SBDs. A high BV of 601 V is obtained with a low on-resistance of 3.15 mΩ·cm2. 相似文献
14.
In this paper, we take account of the spontaneous and piezoelectric polarization effect at the heterointerface in the AlGaN/GaN HEMT device, and one-dimensional Schrödinger–Poisson equations are solved self-consistently using a nonuniform mesh; using our findings, the AlGaN/GaN heterostructure conduction band and the two-dimensional electron gas (2DEG) density are investigated. The dependences of the 2DEG characteristics on the Al fraction, the thickness of each layer, the donor concentration and the gate voltage are investigated through simulation. The output characteristics are simulated using a quasi-2D model; a saturation voltage and threshold voltage are also shown. The influence of the spacer layer width on the 2DEG density is calculated for the first time. An explanation and analyses are given. 相似文献
15.
Channel temperature determination of a multifinger AlGaN/GaN high electron mobility transistor using a micro-Raman technique
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Self-heating in a multifinger AlGaN/GaN high electron mobility transistor (HEMT) is investigated by micro-Raman spectroscopy. The device temperature is probed on the die as a function of applied bias. The operating temperature of the AlGaN/GaN HEMT is estimated from the calibration curve of a passively heated AlGaN/GaN structure. A linear increase of junction temperature is observed when direct current dissipated power is increased. When the power dissipation is 12.75 W at a drain voltage of 15 V, a peak temperature of 69.1°C is observed at the gate edge on the drain side of the central finger. The position of the highest temperature corresponds to the high-field region at the gate edge. 相似文献
16.
Directly extracting both threshold voltage and series resistance from the conductance-voltage curve of an AlGaN/GaN Schottky diode
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An Ni/Au Schottky contact on an AlGaN/GaN heterostructure has been prepared. By using the peak-conductance model, the threshold voltage and the series resistance of the AlGaN/GaN diode are simultaneously extracted from the conductance-voltage (G-V) curve and found to be in good agreement with the ones obtained by using the capacitance-voltage (C-V) curve integration and the plot of dV/d(ln I) versus current I. Thus, a method of directly and simultaneously extracting both the threshold voltage and the series resistance from the conductance-voltage curve for the AlGaN/GaN Schottky diode is developed. 相似文献
17.
Schottky forward current transport mechanisms in AlGaN/GaN HEMTs over a wide temperature range
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The behavior of Schottky contacts in AlGaN/GaN high electron mobility transistors(HEMTs) is investigated by temperature-dependent current–voltage(T –I–V) measurements from 300 K to 473 K. The ideality factor and barrier height determined based on the thermionic emission(TE) theory are found to be strong functions of temperature, while present a great deviation from the theoretical value, which can be expounded by the barrier height inhomogeneities. In order to determine the forward current transport mechanisms, the experimental data are analyzed using numerical fitting method,considering the temperature-dependent series resistance. It is observed that the current flow at room temperature can be attributed to the tunneling mechanism, while thermionic emission current gains a growing proportion with an increase in temperature. Finally, the effective barrier height is derived based on the extracted thermionic emission component, and an evaluation of the density of dislocations is made from the I–V characteristics, giving a value of 1.49 × 107cm-2. 相似文献
18.
19.
In this paper,the influence of a drain field plate(FP)on the forward blocking characteristics of an AlGaN/GaN high electron mobility transistor(HEMT)is investigated.The HEMT with only a gate FP is optimized,and breakdown voltage VBRis saturated at 1085 V for gate–drain spacing LGD≥8μm.On the basis of the HEMT with a gate FP,a drain FP is added with LGD=10μm.For the length of the drain FP LDF≤2μm,VBRis almost kept at 1085 V,showing no degradation.When LDFexceeds 2μm,VBRdecreases obviously as LDFincreases.Moreover,the larger the LDF,the larger the decrease of VBR.It is concluded that the distance between the gate edge and the drain FP edge should be larger than a certain value to prevent the drain FP from affecting the forward blocking voltage and the value should be equal to the LGDat which VBR begins to saturate in the first structure.The electric field and potential distribution are simulated and analyzed to account for the decrease of VBR. 相似文献
20.
E. Iliopoulos M. Zervos A. Adikimenakis K. Tsagaraki A. Georgakilas 《Superlattices and Microstructures》2006,40(4-6):313
Silicon-doped GaN epilayers and AlGaN/GaN heterostructures were developed by nitrogen plasma-assisted molecular beam epitaxy on high resistivity iron-doped GaN (0001) templates and their properties were investigated by atomic force microscopy, x-ray diffraction and Hall effect measurements. In the case of high electron mobility transistors heterostructures, the AlN mole fraction and the thickness of the AlGaN barrier employed were in the range of from 0.17 to 0.36 and from 7.5 to 30 nm, respectively. All structures were capped with a 2 nm GaN layer.Despite the absence of Ga droplets formation on the surface, growth of both GaN and AlGaN by RF-MBE on the GaN (0001) surfaces followed a step-flow growth mode resulting in low surface roughness and very abrupt heterointerfaces, as revealed by XRD. Reciprocal space maps around the reciprocal space point reveal that the AlGaN barriers are fully coherent with the GaN layer.GaN layers, n-doped with silicon in the range from 1015 to 1019 cm−3 exhibited state of the art electrical properties, consistent with a low unintentional background doping level and low compensation ratio. The carrier concentration versus silicon cell temperatures followed an Arhenius behaviour in the whole investigated doping range. The degenerate 2DEG, at the AlGaN/GaN heteroiterfaces, exhibited high Hall mobilities reaching 1860 cm2/V s at 300 K and 10 220 cm2/V s at 77 K for a sheet carrier density of 9.6E12 cm−2.The two dimensional degenerate electron gas concentration in the GaN capped AlGaN/GaN structures was also calculated by self-consistent solving the Schrödinger–Poisson equations. Comparison with the experimental measured values reveals a Fermi level pinning of the GaN (0001) surface at about 0.8 eV below the GaN conduction band. 相似文献