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1.
Effective electron velocities in silicon MOSFETs exceeding the bulk saturation values of 107 cm/s at room temperature and 1.3×107 cm/s at liquid-nitrogen temperature are inferred. This conclusion suggests that electron velocity overshoot occurs over a large portion of the device channel length. To infer this phenomenon, submicrometer-channel-length Si MOSFETs with lightly doped inversion layers were fabricated. These devices have low field mobility of 450 cm2/V-s and showed only slight short-channel effects. Effective carrier velocities are calculated from the saturated transconductance gm at VDS=1.5 V after correction for parasitic resistances of source and drain  相似文献   

2.
n-channel MOSFET's with channel lengths from 75 nm to 5 µm were fabricated in Si using combined X-ray and optical lithographies, and were characterized at 300, 77, and 4.2 K. Average channel electron velocities υewere extracted according to the equationupsilon_{e}=g_{mi}/C_{ox}, where gmiis the intrinsic transconductance and Coxis the capacitance of the gate oxide. We found that at 4.2 K the average electron velocity of a 75-nm-channel MOSFET is 1.7 × 107cm/s, which is 1.8 times higher than the inversion layer saturation velocity reported in the literature, and 1.3 times higher than the saturation velocity in bulk Si at 4.2 K. As channel length increases, the average electron velocity drops sharply below the saturation velocity in bulk Si. These experimental results strongly suggest velocity overshoot in a 75-nm-channel MOSFET.  相似文献   

3.
The authors report on the fabrication and the resultant device characteristics of the first 0.25-μm gate-length field-effect transistor based on n-type modulation-doped Si/SiGe. Prepared using ultrahigh vacuum/chemical vapor deposition (UHV/CVD), the mobility and electron sheet charge density in the strained Si channel are 1500 (9500) cm2/V-s and 2.5×1012 (1.5×1012 ) cm-2 at 300 K (77 K). At 77 K, the devices have a current and transconductance of 325 mA/mm and 600 mS/mm, respectively. These values far exceed those found in Si MESFETs and are comparable to the best results achieved in GaAs/AlGaAs modulation-doped transistors  相似文献   

4.
Ge-channel modulation-doped field-effect transistors (MODFET's) with extremely high transconductance are reported. The devices were fabricated on a compressive-strained Ge/Si0.4Ge0.6 heterostructure with a Hall mobility of 1750 cm2/Vs (30,900 cm2/Vs) at room temperature (77 K). Self-aligned, T-gate p-MODFET's with Lg=0.1 μm displayed an average peak extrinsic transconductance (g(mext)) of 439 mS/mm, at a drain-to-source bias voltage (Vds) of -0.6 V, with the best device having a value of g(mext)=488 mS/mm. At 77 K, values as high as g(mext)=687 mS/mm were obtained at a bias voltage of only Vds=-0.2 V. These devices also displayed a unity current gain cutoff frequency (fT) of 42 GHz and maximum frequency of oscillation (fmax) of 86 GHz at Vds=-0.6 V and -1.0 V, respectively  相似文献   

5.
Quantum-well p-channel pseudomorphic AlGaAs/InGaAs/GaAs heterostructure insulated-gate field-effect transistors with enhanced hole mobility are described. The devices exhibit room-temperature transconductance, transconductance parameter, and maximum drain current as high as 113 mS/mm, 305 mS/V/mm, and 94 mA/mm, respectively, in 0.8-μm-gate devices. Transconductance, transconductance parameter, and maximum drain current as high as 175 mS/mm, 800 mS/V/mm, and 180 mA/mm, respectively were obtained in 1-μm p-channel devices at 77 K. From the device data hole field-effect mobilities of 860 cm2/V-s at 300 K and 2815 cm2/V-s at 77 K have been deduced. The gate current causes the transconductance to drop (and even to change sign) at large voltage swings. Further improvement of the device characteristics may be obtained by minimizing the gate current. To this end, a type of device structure called the dipole heterostructure insulated-gate field-effect transistor is proposed  相似文献   

6.
The fabrication and performance of dummy-gate self-aligned germanium MOSFETs utilizing a native germanium oxynitride gate insulator is reported. Based on device characteristics, channel mobility at 300 K is estimated as 940 cm2/Vs. Common-source characteristics show good saturation and turn-off, and do not exhibit looping or other anomalies. It is felt these results suggest that integration of germanium MOSFETs with photodiodes for monolithic optical-fiber receivers operating at 1.3-μm wavelength should be possible. The results also indicate that the bulk mobility advantage which germanium exhibits relative to silicon carries over in some measure to FET channel mobility  相似文献   

7.
A new process, electron cyclotron resonance (ECR) microwave plasma oxidation, has been developed to produce a gate-quality oxide directly on SiGe alloys. One μm Al gate Si0.86Ge0.15 p-metal-oxide-semiconductor field-effect-transistors (pMOSFET's) with ECR-grown gate oxide have been fabricated. It is found that saturation transconductance increases from 48 mS/mm at 300 K to 60 mS/mm at 77 K. Low field hole mobilities of 167 cm2/V-s at 300 K and 530 cm 2/V-s at 77 K have been obtained  相似文献   

8.
A novel subsurface SiGe-channel p-MOSFET is demonstrated in which modulation doping is used to control the threshold voltage without degrading the channel mobility. A novel device design consisting of a graded SiGe channel, an n+ polysilicon gate, and p+ modulation doping is used. A boron-doped layer is located underneath the graded and undoped SiGe channel to minimize process sensitivity and maximize transconductance. Low-field hole mobilities of 220 cm2/V-s at 300 K and 980 cm2/V-s at 82 K were achieved in functional submicrometer p-MOSFETs  相似文献   

9.
Nonequilibrium electron transport in InGaAs pseudomorphic MODFETs has been analyzed with the moment equations approach. In the model, the momentum and energy balance equations for the two-dimensional electrons in the InGaAs channel are solved with relaxation times generated from a Monte Carlo simulation. The two-dimensional electron wave functions and the quantized state energies in the InGaAs quantum well are calculated exactly from the Schrodinger equation along the direction perpendicular to the quantum well. Also included is a two-dimensional Poisson equation solver. In the calculation, all of the equations are solved iteratively until a self-consistent solution is achieved. The simulation results for a realistic device structure with a 0.5-μm recessed gate show a significant overshoot velocity of 4.5×107 cm/s at a drain bias of 1.0 V. Electron temperature reaches a peak value of around 2500 K under the gate. In energy transport, the diffusive component of the energy flux is found to be dominant in the high-field region  相似文献   

10.
This letter describes the material characterization and device test of InAlAs/InGaAs high electron mobility transistors (HEMTs) grown on GaAs substrates with indium compositions and performance comparable to InP-based devices. This technology demonstrates the potential for lowered production cost of very high performance devices. The transistors were fabricated from material with room temperature channel electron mobilities and carrier concentrations of μ=10000 cm2 /Vs, n=3.2×1012 cm-2 (In=53%) and μ=11800 cm2/Vs, n=2.8×1012 cm-2 (In=60%). A series of In=53%, 0.1×100 μm2 and 0.1×50 μm2 devices demonstrated extrinsic transconductance values greater than 1 S/mm with the best device reaching 1.074 S/mm. High-frequency testing of 0.1×50 μm2 discrete HEMT's up to 40 GHz and fitting of a small signal equivalent circuit yielded an intrinsic transconductance (gm,i) of 1.67 S/mm, with unity current gain frequency (fT) of 150 GHz and a maximum frequency of oscillation (fmax) of 330 GHz. Transistors with In=60% exhibited an extrinsic gm of 1.7 S/mm, which is the highest reported value for a GaAs based device  相似文献   

11.
High-mobility strained-Si PMOSFET's   总被引:1,自引:0,他引:1  
Operation and fabrication of a new high channel mobility strained-Si PMOSFET are presented. The growth of high-quality strained Si layer on completely relaxed, step-graded, SiGe buffer layer is demonstrated by gas source MBE. The strained-Si layer is characterized by double crystal X-ray diffraction, photoluminescence, and transmission electron microscopy. The operation of a PMOSFET is shown by device simulation and experiment. The high-mobility strained-Si PMOSFET is fabricated on strained-Si, which is grown epitaxially on a completely relaxed step-graded Si0.82Ge0.18 buffer layer on Si(100) substrate. At high vertical fields (high |Vg|), the channel mobility of the strained-Si device is found to be 40% and 200% higher at 300 K and 77 K, respectively, compared to those of the bulk Si device. In the case of the strained-Si device, degradation of channel mobility due to Si/SiO2 interface scattering is found to be more pronounced compared to that of the bulk Si device. Carrier confinement at the type-II strained-Si/SiGe-buffer interface is clearly demonstrated from device transconductance and C-V measurements at 300 K and 77 K  相似文献   

12.
From saturation transconductance of devices of 0.25-μm CMOS technology, the saturation velocity of electrons (νsat) in the inversion layer from 90 to 350 K has been determined. The extracted νsat at 300 K was 7.86×106 cm/s, which is significantly lower than that of bulk silicon (νsat-blk) and has a much weaker temperature dependence. The ratio νsat-blk sat is 1.27 at 300 K, and is increased to 1.68 at 90 K. Consistent values of νsat have been determined for devices of three vastly different MOS technologies, demonstrating the technology independence of νsat. The results are useful for developing and testing theoretical carrier transport models, and are of practical importance in estimating the ultimate speed performance of surface MOSFETs. An empirical model for νsat as a function of temperature has also been derived for application in predictive device simulation  相似文献   

13.
A new Si thin-film transistor (TFT) has been proposed where only one grain-boundary exists at the center of channel, and the source and drain are within single grains with good crystallinity. The device fabricated by an excimer-laser crystallization method at the maximum temperature of 500°C, had the on-off current ratio ≅106 , the field-effect mobility ≅330 cm2/Vs and the subthreshold swing ≅1.1 V/dec, respectively, For the device processed at 800°C, they are >106, >450 cm2 /Vs and ≅0.51 V/dec, respectively  相似文献   

14.
This letter describes high electron mobility transistors (HEMT's) utilizing a conducting channel which is a single In0.15Ga0.85AS quantum well grown pseudomorphically on a GaAs substrate. A Hall mobility of 40 000 cm2/V.s has been observed at 77 K. Shubnikov-de Haas oscillations have been observed at 4.2 K which verify the existence of a two-dimensional electron gas at the In0.15Ga0.85As/GaAs interface. HEMT's fabricated with 2-µm gate lengths show an extrinsic transconductance of 90 and 140 mS/mm at 300 and 77 K, respectively-significantly larger than that previously reported for strained-layer superlattice InxGa1-xAs structures which are nonpseudomorphic to GaAs substrates. HEMT's with 1-µm gate lengths have been fabricated, which show an extrinsic transconductance of 175 mS/mm at 300 K which is higher than previously reported values for both strained and unstrained InxGa1-xAs FET's. The absence of AlxGa1-xAs in these structures has eliminated both the persistent photoconductivity effect and drain current collapse at 77 K.  相似文献   

15.
Operation of the first AlSbAs/GaSb p-channel modulation-doped field-effect transistor (MODFET) is reported. Devices with 1-μm gate length exhibit transconductance of 30 and 110 mS/mm at room temperature and 80 K, with respective maximum drain current densities of 25 and 80 mA/mm. The low field Hall mobility and sheet carrier density of this modulation doped structure were 260 cm2/V-s and 1.8×10 12 cm-2 at room temperature and 1700 cm2/V-s and 1.4×1012 cm-2 at 77 K. Calculations based on these results indicate that room-temperature transconductances of 200 mS/mm or greater could be achieved. This device can be integrated with an InAs n-channel HFET for complementary circuit applications  相似文献   

16.
This letter reports a new and high-performance InGaP/InxGa1-xAs high electron mobility transistor (HEMT) with an inverted delta-doped V-shaped channel. Due to the presence of V-shaped inverted delta-doped InGaP/InxGa1-x As structure, good carrier confinement and a flat and wide transconductance operation regime are expected. Experimentally, the fabricated device (1×100 μm2) shows a high gate-to-drain breakdown voltage of 30 V and a high output drain saturation current density of 826 mA/mm at VGS=2.5 V. The high transconductance expands over a very broad operation range with the maximum value of 201 mS/mm at 300 K. Meanwhile, the studied device exhibits a good microwave frequency linearity  相似文献   

17.
A novel approach that can reduce the thermal budget in the fabrication of thin film transistors (TFTs) using a Si/Si0.7Ge0.3/Si triple film as an active layer was proposed. The crystallization behavior of the triple film was described and device characteristics of Si/Si0.7Ge0.3 /Si TFTs were compared with those of Si TFTs and of SiGe TFTs. The triple film was completely crystallized only after a 25-h anneal at 550°C. N-channel polycrystalline Si/Si0.7Ge0.3/Si TFTs had a field-effect mobility of 57.9 cm2/Vs and an Ion/Ioff ratio of 5.7×106. This technique provides not only a shorter time processing capability than Si TFT's technology but also superior device characteristics compared to SiGe TFTs  相似文献   

18.
The theoretical study of a novel Si/SiGe structure combining the advantages of buried channel MOS devices and conventional SiGe FET's is presented. A self-consistent one-dimensional Schrodinger-Poisson simulator has been developed to evaluate the gate dependence of electron effective mobility in the zero-field limit. Room temperature peak mobility values greater than 2800 cm2/Vs are predicted. The proposed structure shows also good turn-on characteristic and linear transconductance behavior, which represents a significant feature in view of possible technology applications  相似文献   

19.
Si-delta-doped Al0.25Ga0.75As/InxGa1-xAs (x=0.15-0.28) P-HEMT's, prepared by LP-MOCVD, are investigated. The large conduction band discontinuity leads to 2-DEG density as high as 2.1×1012/cm2 with an electron mobility of 7300 cm2/V·s at 300 K. The P-HEMT's with 0.7×60 μm gate have a maximum extrinsic transconductance of 380 mS/mm, and a maximum current density of 300 mA/mm. The S-parameter measurements indicate that the current gain and power gain cutoff frequencies are 30 and 61 GHz, respectively, The RF noise characteristics exhibit a minimum noise figure of 1.2 dB with an associated gain of 10 dB at 10 GHz. Due to the efficient doping technique, the electron mobility and transconductance obtained are among the best reported for MOCVD grown P-HEMT's with the similar structure  相似文献   

20.
The two-dimensional electron gas in InP/GaInAs heterojunctions, grown by LP-OMVPE, showed Hall mobilities as high as 164000 and 103000 cm2/Vs at 4 K and 80 K, respectively. A maximum Hall mobility of 172000 cm2/Vs was measured at 20 K. Shubnikov-de Haas oscillations measured at 200 mK in magnetic fields up to 20 T indicated the total absence of parallel conduction. By illuminating the sample it was possible to populate the second electrical sub-band at a total carrier density ns=4.4×1011 cm-2  相似文献   

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