D.G. Hayes

High-performance 40nm gate length InSb p-channel compressively strained quantum well field effect transistors for low-power (VCC=0.5V) logic applications

This paper describes for the first time, a high-speed and low-power III-V p-channel QWFET using a compressively strained InSb QW structure. The InSb p-channel QW device structure, grown using solid source MBE, demonstrates a high hole mobility of 1,230 cm2/V-s. The shortest 40 nm gate length (LG) transistors achieve peak transconductance (Gm) of 510 muS/mum and cut-off frequency (fT) of 140 GHz at supply voltage of 0.5V. These represent the highest Gm and fT ever reported for III-V p-channel FETs. In addition, effective hole velocity of this device has been measured and compared to that of the standard strained Si p-channel MOSFET.

85nm gate length enhancement and depletion mode InSb quantum well transistors for ultra high speed and very low power digital logic applications

We demonstrate for the first time 85nm gate length enhancement and depletion mode InSb quantum well transistors with unity gain cutoff frequency, fT, of 305 GHz and 256 GHz, respectively, at 0.5V VDS, suitable for high speed, very low power logic applications. The InSb transistors demonstrate 50% higher unity gain cutoff frequency, fT, than silicon NMOS transistors while consuming 10 times less active power

Novel InSb-based quantum well transistors for ultra-high speed, low power logic applications

InSb-based quantum well field-effect transistors, with gate length down to 0.2 /spl mu/m, are fabricated for the first time. Hall measurements show that room temperature electron mobilities over 30,000 cm /sup 2/V/sup -1/s/sup -1/ are achieved with a sheet carrier density over 1/spl times/10/sup 12/ cm/sup -2/ in a modulation doped InSb quantum well with Al/sub x/In/sub 1-x/Sb barrier layers. Devices with 0.2 /spl mu/m gate length and 20% Al barrier exhibit DC transconductance of 625 /spl mu/S//spl mu/m and f/sub T/ of 150 GHz at V/sub DS/ =0.5V. 0.2 /spl mu/m devices fabricated on 30% Al barrier material show DC transconductance of 920 /spl mu/S//spl mu/m at V/sub DS/ = 0.5 V. Benchmarking against state-of-the-art Si MOSFETs indicates that InSb QW transistors can achieve equivalent high speed performance with 5-10 times lower dynamic power dissipation and therefore are a promising device technology to complement scaled silicon-based devices for very low power, ultra-high speed logic applications.

Analysis of DC–RF Dispersion in AlGaN/GaN HFETs Using RF Waveform Engineering

This paper describes how dc-radio-frequency (RF) dispersion manifests itself in AlGaN/GaN heterojunction field-effect transistors when the devices are driven into different RF load impedances. The localized nature of the dispersion in the I-V plane, which is confined to the ldquokneerdquo region, is observed in both RF waveform and pulsed I-V measurements. The effect is fully reproduced using 2-D physical modeling. The difference in dispersive behaviors has been attributed to the geometry of a trap-induced virtual-gate region and the resulting carrier velocity saturation being overcome by punchthrough effects under high electric fields.

On the temperature and carrier density dependence of electron saturation velocity in an AlGaN/GaN HEMT

The temperature and carrier density dependence of electron intrinsic saturation velocity (v/sub si/) in a 0.3-/spl mu/m gate length AlGaN/GaN HEMT was extracted from multibias S-parameter measurements. It was found that v/sub si/ fell rapidly with increasing sheet carrier concentration (n/sub s/), but was only a very weak function of ambient temperature (T/sub amb/). This behavior is consistent with the hot-phonon model of carrier transport.

Control of Short-Channel Effects in GaN/AlGaN HFETs

GaN/AlGaN HEMTs can suffer from short channel effects as a result of insufficient buffer doping. The paper show that controlled iron doping of the GaN buffer during MOVPE growth can suppress all short-channel effects in 0.25mum gate length devices. The authors show that optimised iron doping has no effect on the RF output power or on the knee walkout (current-slump), but significantly improves the power added efficiency

High-performance InSb based quantum well field effect transistors for low-power dissipation applications

Indium antimonide (InSb) has the highest electron mobility and saturation velocity of any conventional semiconductor, giving potential for a range of analogue and digital ultra-high speed, low power dissipation applications. N-channel quantum well FETs have been fabricated with current gain cut-off frequency (fT) of more than 250 GHz and power gain cut-off frequency (fmax) of 500 GHz. Outline designs confirm the potential for multi-stage low noise amplifiers operating at more than 200 GHz, for applications such as integrated passive millimetre wave imaging.

Detailed Analysis of DC-RF Dispersion in AlGaN/GaN HFETs using Waveform Measurements

Detailed time-domain IV waveforms at RF frequencies are employed for characterisation of AlGaN/GaN HFETs in order to steer and advance device development. The IV time-domain data is used to isolate the separate effects of pinch-off and knee-walkout behaviour in limiting device performance. Furthermore, the waveform measurements which are obtained with a previously unseen level of detail, allowed the direct extraction of optimum device operating conditions

GaN devices for microwave applications [FET/HEMT]

AlGaN/GaN field effect transistors offer spectacular improvements in performance compared to conventional III-V components. In particular they are well suited to applications requiring high levels of output power and are capable of producing RF output power levels approaching 12 W/mm of gate periphery with power added efficiency close to theoretical limits. This paper describes the current status of GaN based FETs and discusses circuit functions and system applications that can benefit from this disruptive technology.

Indium Antimonide Based Technology for RF Applications

Indium antimonide has the highest electron mobility and saturation velocity of any semiconductor, so gives the prospect of extremely high frequency operation with very low power dissipation. We report uncooled transistors with cut-off frequency of 340 GHz at a source-drain voltage of 0.5 V, leading towards this goal