M. T. Emeny

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

Inter-sub-band absorption in GaAs/AlGaAs single quantum wells

The observation of resonant inter-sub-band absorption in AlxGa1-xAs/GaAs single quantum wells using a total internal reflection geometry is reported. It is shown that strong absorption is obtained provided that a large optical electrical field perpendicular to the quantum wells is generated. Such conditions occur when the well is close to the reflecting boundary and reflection occurs at a semiconductor/metal interface, but not when reflection occurs at a semiconductor/vacuum interface. The optical properties of the whole structure can be quantitatively described by considering the system as a multi-layer dielectric stack.

Mid-infrared AlxIn1−xSb light-emitting diodes

The properties of AlxIn1−xSb light-emitting diodes (LEDs) have been investigated as a function of aluminum concentrations between 0% and 8.8%. By varying the aluminum concentration it is possible to tailor the peak emission wavelength to match the characteristic absorption of CO2, CO, CH4, NO, and NO2, making these diodes suitable for use in infrared gas sensing applications. The total emitted power and internal quantum efficiency were found to have maxima of 27mW∕cm2 and 4.2%, respectively, at a composition of 2.5%, where the peak emission was found to be 5.3μm, making LEDs of this composition particularly suited to the detection of NO.

Midinfrared GaInSb/AlGaInSb quantum well laser diodes operating above 200 K

Electroluminescence from GaInSb/AlGaInSb type I quantum well diode lasers, grown on GaAs, has been investigated as a function of strain in the quantum wells. Lasing was observed, in pulsed operation, up to temperatures of 161, 208, 219, and 202 K for structures containing 0.55%, 0.62%, 0.78%, and 1.1% strain, respectively, with lasing occurring at ∼3.3 μm at 200 K for the 1.1% structure.

InSb/AlInSb quantum-well light-emitting diodes

We have investigated the room-temperature electroluminescent properties of InSb∕AlxIn1−xSb quantum-well light-emitting diodes. The maximum emission from diodes containing quantum wells occurred at significantly higher energies than the band gap of InSb. Close agreement between experimental and theoretical data confirms that recombination occurs within the quantum well.

Optimizing indium aluminum antimonide LEDs and photodiodes for gas sensing applications

We have developed a range of un-cooled mid-IR LEDs and photodiodes for IR gas sensing applications. Varying the composition of MBE grown Indium Aluminium Antimonide (In(1-x)AlxSb) epi-layers on GaAs allows us to engineer the emission/detection wavelength for a particular gas up to λmax≈6μm. The relatively high series resistance, LED drive requirements, and the non-optimised impedance matching of the un-biased photodiodes restricts the market for these components. Sub-dividing single element devices into N smaller devices connected in series enable the LED current and voltage requirements to be tailored to match the source, and improves the photodiode impedance matching. We report the development of the necessary growth and photolithography technologies for series-connecting InAlSb diodes on GaAs substrates. We include results from multi-element Co2 (Al(x)=4.5%) and CH4 (Al(x)=8.5%) sensing LEDs and photodiodes. These impedance matched LEDs represent a 9-fold improvement in the wall-plug efficiency compared with single element LEDs with the same light output. The impedance of the multi-element photodiodes is increased significantly with respect to the series resistance, which gives up to a 5-fold improvement in sensitivity since the noise contributions from the external amplifier and series resistance are minimised. These advances have greatly improved the suitability of these components for gas sensing, and further improvements in the performance are expected through optimisation of the epi-layer design and the device geometry.

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.

Recombination processes in midinfrared AlxIn1−xSb light-emitting diodes

Emission characteristics, spectral properties, and quantum efficiencies of AlxIn1−xSb light-emitting diodes, with aluminum compositions between 0% and 8.75%, have been investigated as a function of temperature from 25 to 300 K, and a function of current from 1 to 100 mA. As both current and temperature are varied a change in the dominant recombination mechanism is observed as indicated by changes in the measured emission. An analysis of the light-current characteristics shows that Auger processes become important in all devices at temperatures above 100 K, implying an activation energy of approximately 7–13 meV depending on the aluminum composition.

Lateral light emitting n-i-p diodes in InSb∕AlxIn1−xSb quantum wells

Lateral light emitting diodes have been fabricated in InSb∕AlxIn1−xSb quantum wells using a simple bevel etching technique. The peak in emission was found to be in the range of 4–5μm, confirming that the emission was from the quantum well.