高性能的增强型AlGaN/GaN HEMT

采用氟离子处理的方法实现了阈值电压0.35V的增强型AlGaN/GaN HEMT 器件。该器件展示了高性能直流特性,最大饱和电流 667mA/mm,器件的峰值跨导达到203ms/mm。 1μm栅长电流增益截止频率和最大振荡截止频率分别为10.3GHz和12.5GHz,并且小信号特性在器件氟离子处理后并没有出现衰退。最后,采用SIMS的实验结果辅助进行了数值仿真,对氟离子在势垒层中起受主缺陷的理论给出了合理的解释。     

A high-performance enhancement-mode AIGaN/GaN HEMT

An enhancement-mode AlGaN/GaN HEMT with a threshold voltage of 0.35 V was fabricated by fluorine plasma treatment.The enhancement-mode device demonstrates high-performance DC characteristics with a saturation current density of 667 mA/mm at a gate bias of 4 V and a peak transconductance of 201 mS/mm at a gate bias of 0.8 V. The current-gain cut-off frequency and the maximum oscillation frequency of the enhancement-mode device with a gate length of 1μm are 10.3 GHz and 12.5 GHz,respectively,which is compa...     

A high-performance enhancement-mode AlGaN/GaN HEMT

An enhancement-mode AlGaN/GaN HEMT with a threshold voltage of 0.35 V was fabricated by fluorine plasma treatment.The enhancement-mode device demonstrates high-performance DC characteristics with a saturation current density of 667 mA/mm at a gate bias of 4 V and a peak transconductance of 201 mS/mm at a gate bias of 0.8 V.The current-gain cut-off frequency and the maximum oscillation frequency of the enhancement-mode device with a gate length of μm are 10.3 GHz and 12.5 GHz,respectively,which is comparable with the depletion-mode device.A numerical simulation supported by SIMS results was employed to give a reasonable explanation that the fluorine ions act as an acceptor trap center in the barrier layer.     

Enhancement-mode pseudomorphic inverted HEMT for low noiseamplifier

Characteristics of the pseudomorphic inverted HEMT (P-I-HEMT) are compared with those of the pseudomorphic HEMT. Both devices were fabricated in enhancement mode by the same process. P-I-HEMT shows a higher maximum transconductance of 590 mS/mm, and higher K-value of 600 mS/Vmm at a threshold voltage of O V, and better pinch-off characteristics than its counterpart. Noise characteristics of P-I-HEMT are reported. Lower noise figure (1.0 dB at 18 GHz) was obtained in the P-I-HEMT. It is concluded that the P-I-HEMT shows far better noise characteristics than the other at low drain voltage and current     

A voltage-controlled ring oscillator using InP full enhancement-mode HEMT logic

A voltage-controlled ring oscillator (VCO) based on a full enhancement-mode InAIAs/InGaAs/InP high electron mobility transistor (HEMT) logic is proposed. An enhancement-mode HEMT (E-HEMT) is fabricated, whose threshold is demonstrated to be 10 mV. The model of the E-HEMT is established and used in the SPICE simulation of the VCO. The result proves that the full E-HEMT logic technology can be applied to the VCO. And compared with the HEMT DCFL technology, the complexity of our fabrication process is reduced and the reliability is improved.     

Recessed-gate AlGaAs-InGaAs-GaAs pseudomorphic HEMT withSi-planar-doped etch stop layer

An improved slot etch technique based on an Si planar doped layer has been applied to gate recessing in the fabrication of AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistors (HEMTs). The devices exhibited comparable g_m with much better breakdown and leakage behaviour than conventional pseudomorphic HEMT devices     

Cryogenic characteristics of wide-band pseudomorphic HEMT MMIClow-noise amplifiers

Two wideband (8-18-GHz) single-stage MMIC (monolithic microwave integrated circuit) low-noise amplifiers (LNAs) using 0.2-μm T-gate InGaAs pseudomorphic HEMT (high-electron-mobility transistor) technology, designed and fabricated for room temperature operation, were evaluated and compared at cryogenic temperatures below 20 K. One is a balanced design using 3-dB Lange couplers, and the other is a feedback design using a series RLC parallel feedback network. The gain flatness over the 8-18-GHz frequency band was maintained for both amplifiers at room and cyrogenic temperatures, indicating that the topology for wideband designs is insensitive to temperature of operation. As the physical temperature decreased from 297 K to below 20 K, the balanced LNA exhibited an average gain increase of 2 dB and as much as an eightfold reduction of noise temperature to 20 K, while the feedback LNA exhibited an average gain increase of less than 1 dB and an average foufold reduction of noise temperature to 50 K. The negative feedback network of the feedback LNA resulted in less gain increase and less noise temperature reduction at cryogenic temperatures     

A high-gain, low-noise 1/2-μm pulse-doped pseudomorphic HEMT

A 1/2-μm gate-length pulse-doped pseudomorphic high-electron-mobility transistor (HEMT) grown by MBE, which exhibits a current-gain cutoff frequency of 62 GHz, is discussed. The maximum available gain cutoff frequency was greater than 150 GHz. A minimum noise figure of 0.85 dB and associated gain of 14 dB were measured at 10 GHz. Tuned small-signal gain in a waveguide-to-microstrip test fixture at 44 GHz was 7.6 dB. When the HEMT was tuned for power, 260 mW/mm with 5-dB gain and 17% power-added efficiency were obtained at 44 GHz. These results suggest that a 1/2-μm pseudomorphic HEMT is a viable candidate for Q-band applications     

MBE growth of pseudomorphic HEMT structures for MMIC applications

The development of the GaAs metal semiconductor field effect transistor (MESFET) in the 1960s allowed integrated circuits operating at microwave frequencies to be fabricated. GaAs foundries can now produce customer circuit designs operating up to 20 GHz, using an implanted MESFET process. The push to higher operating frequencies, higher gains and lower noise figures has led to the development of the high electron mobility transistor (HEMT) and the pseudomorphic HEMT. This paper describes how molecular beam epitaxy (MBE) has been used to produce material for pseudomorphic HEMT circuits and how the epitaxial process influences device yield and device performance.     

基于InP全增强HEMT逻辑的环形压控振荡器研究

A voltage-controlled ring oscillator （VCO） based on a full enhancement-mode InAlAs/InGaAs/InP high electron mobility transistor （HEMT） logic is proposed. An enhancement-mode HEMT （E-HEMT） is fabricated, whose threshold is demonstrated to be 10 mV. The model of the E-HEMT is established and used in the SPICE simulation of the VCO. The result proves that the full E-HEMT logic technology can be applied to the VCO. And compared with the HEMT DCFL technology, the complexity of our fabrication process is reduced and the reliability is improved.     

InP-based enhancement-mode pseudomorphic HEMT with strainedIn0.45Al0.55As barrier andIn0.75Ga0.25As channel layers

Using strained aluminum-rich In_0.45Al_0.55As as Schottky contact materials to enhance the barrier height and indium-rich In_0.75Ga_0.25As as channel material to enhance the channel performance, we have developed InP-based enhancement-mode pseudomorphic InAlAs/InGaAs high electron mobility transistors (E-PHEMT's) with threshold voltage of about 170 mv. A maximum extrinsic transconductance of 675 mS/mm and output conductance of 15 mS/mm are measured respectively at room temperature for 1 μm-gate-length devices, with an associated maximum drain current density of 420 mA/mm at gate voltage of 0.9 V. The devices also show excellent rf performance with cutoff frequency of 55 GHz and maximum oscillation frequency of 62 GHz. To the best of the authors' knowledge, this is the first time that InP-based E-PHEMT's with strained InAlAs barrier layer have been demonstrated     

Determining intrinsic noise parameters of 0.25 mu m gate pseudomorphic HEMT

An accurate equivalent circuit of a pseudomorphic HEMT (PM-HEMT) has been used, together with physically realistic values for the intrinsic PM-HEMT noise parameters (P, R, and C) to estimate the extrinsic noise parameters (minimum noise figure, optimum noise impedance, etc.) of a 0.25 mu m gate PM-HEMT. It is demonstrated that good agreement with experiment can be obtained for the minimum noise figure, optimum noise impedance, and also noise resistance, over the frequency range 6-18 GHz.<>     

New evidence for velocity overshoot in a 200 nm pseudomorphic HEMT

It is believed that significant velocity overshoot effects are responsible for the high performance of pseudomorphic HEMTs (PsHEMTs). The overshoot is associated with the low effective mass in the InGaAs channel and the large Γ-L separation. Average channel electron velocities well in excess of 3.0 × 10⁷ cm/s have been predicted in Monte-Carlo PsHEMT simulations. However, average electron velocities extracted from transconductance measurements of such devices are much lower, typically in the range 1.5–2.0 × 10⁷ cm/s. In this paper we analyse real device measurements by using Monte-Carlo and drift diffusion simulations. We show clear evidence that the average velocity in the channel of a 200 nm PsHEMT fabricated in the Nano-electronics Research Centre of Glasgow University exceeds 3.0 × 10⁷ cm/s.     

DC and RF characteristics of enhancement-mode InAIN/GaN HEMT with fluorine treatment

We report an enhancement-mode InA1N/GaN HEMT using a fluorine plasma treatment. The threshold voltage was measured to be ＋0.86 V by linear extrapolation from the transfer characteristics. The transconductance is 0 mS/mm at Vc, s = 0 V and VDS = 5 V, which shows a truly normal-offstate. The gate leakage current density of the enhancement-mode device shows two orders of magnitude lower than that of the depletion-mode device. The transfer characteristics of the E-mode InA1N/GaN HEMT at room temperature and high temperature are reported. The current gain cut-off frequency （fT） and the maximum oscillation frequency （fmax） of the enhancement-mode device with a gate length of 0.3 #m were 29.4 GHz and 37.6 GHz respectively, which is comparable with the depletion-mode device. A classical 16 elements small-signal model was deduced to describe the parasitic and the intrinsic parameters of the device.     

氟处理增强型InAlN/GaN HEMT直流和射频特性分析

报道了使用氟处理的方法制备的InAlN/GaN 增强型器件。 器件的阈值电压为0.86V。 在VGS=0 V ,VDS=5 V下得到器件跨导为0mS, 表现出了完全的关态特性。氟处理之后器件的栅漏电得到了降低。0.3μm栅长器件的电流截至频率（fT）与最大振荡频率(fMAX)分别为29.4GHz和36.7GHz。建立了器件的小信号模型用来描述器件本征与寄生参量。     

High-power V-band pseudomorphic InGaAs HEMT

The author's present the DC and RF power performance of planar-doped channel InGaAs high-electron-mobility transistors (HEMTs). The planar-doped channel (PDC) pseudomorphic GaAs HEMT with 400 μm of gate width exhibited an output power of 184 mW, corresponding to 460 mW/mm, with 4.6-dB saturation gain and 25% power-added efficiency at 55 GHz. Although higher power density is possible, the authors have designed the device to operate at less than 500 mW/mm for thermal and reliability reasons. Devices with unit gate finger widths ranging from 30 to 50 μm were fabricated and characterized, with no performance degradation observed from using the longer gate fingers     

Device and material properties of pseudomorphic HEMT structuressubjected to rapid thermal annealing

The device-related effects of rapid thermal annealing (RTA) on the electrical and optical properties of planar-doped AlGaAs/InGaAs/GaAs high-electron-mobility transistor structures grown by molecular beam epitaxy were investigated. Specifically, electrical and optical characterization techniques such as capacitance versus voltage, current versus voltage, Hall effect, and photoluminescence have been applied to study the effects that typical III-V compound semiconductor rapid thermal processes (RTPs) have on the properties of pseudomorphic AlGaAs/InGaAs/GaAs structures for two different values of In mole fraction content. The effect and stability of the indium mole fraction on both heterostructure and device integrity with respect to RTA schedule has been investigated in detail     

Ensemble Monte Carlo simulation of a 0.35-μm pseudomorphic HEMT

Theoretical analysis and precise comparison to experiment of the performance of a 0.35-μm pseudomorphic Al_0.15Ga_0.85 As/In_0.15Ga_0.85As high-electron-mobility transistor (HEMT) are presented. The calculations are made using an ensemble Monte Carlo simulation with the unique inclusion of real space transfer as well as the full details of the two-dimensional electron gas, velocity overshoot, and ballistic transport, and the effects of the two-dimensional electric field profile. The calculated current-voltage characteristic is compared to recent experimental measurements showing excellent agreement to within ~10% over a full range of gate and drain biases. It is found that near the source, the two-dimensional system dominates the transport physics, while near the pinch-off point, the effects of real space transfer become apparent. It is further determined that the high-speed performance of the pseudomorphic HEMT stems predominantly from the high electron confinement within the two-dimensional system, and the high electron mobility and confinement within the gamma valley in the bulk InGaAs     

Electrical characteristics of an optically controlled N-channelAlGaAs/GaAs/InGaAs pseudomorphic HEMT

Electrical characteristics of an n-channel Al_0.3Ga_0.7As/GaAs/In_0.13Ga_0.87 As pseudomorphic HEMT (PHEMT) with L_g=1 μm on GaAs are characterized under optical input (P_opt). Gate leakage and drain current have been analyzed as a function of V_GS, V _DS, and P_opt. We observed monotonically increasing gate leakage current due to the energy barrier lowering by the optically induced photovoltage, which means that gate input characteristics are significantly limited by the photovoltaic effect. However, we obtained a strong nonlinear photoresponsivity of the drain current, which is limited by the photoconductive effect. We also proposed a device model with an optically induced parasitic Al_0.3Ga_0.7As MESFET parallel to the In_0.13Ga_0.87As channel PHEMT for the physical mechanism in the drain current saturation under high optical input power     

Control of threshold voltage and improved subthreshold swing in enhancement-mode InGaP/InGaAs metal-oxide-semiconductor pseudomorphic high-electron-mobility transistor

The InGaP/InGaAs metal-oxide-semiconductor pseudomorphic high-electron-mobility transistor (MOS-PHEMT) with an oxidized GaAs gate by liquid phase oxidation (LPO) is demonstrated. With the help of the LPO, the threshold voltage (V_th) can be shifted positively to 0.07 V, and enhancement-mode MOS-PHEMT is fabricated. The device with a gate metal of 1 × 100 μm² shows a maximum transconductance of 171 mS/mm at V_DS = 5 V and a maximum drain current density of 182 mA/mm at V_GS = 2 V. It also exhibits a lower leakage current and an improved subthreshold swing compared to the referenced Schottky-gate InGaP/InGaAs PHEMT.