Mikael Egard

Vertical InAs nanowire wrap gate transistors with f(t) > 7 GHz and f(max) > 20 GHz.

In this letter we report on high-frequency measurements on vertically standing III-V nanowire wrap-gate MOSFETs (metal-oxide-semiconductor field-effect transistors). The nanowire transistors are fabricated from InAs nanowires that are epitaxially grown on a semi-insulating InP substrate. All three terminals of the MOSFETs are defined by wrap around contacts. This makes it possible to perform high-frequency measurements on the vertical InAs MOSFETs. We present S-parameter measurements performed on a matrix consisting of 70 InAs nanowire MOSFETs, which have a gate length of about 100 nm. The highest unity current gain cutoff frequency, f(t), extracted from these measurements is 7.4 GHz and the maximum frequency of oscillation, f(max), is higher than 20 GHz. This demonstrates that this is a viable technique for fabricating high-frequency integrated circuits consisting of vertical nanowires.

High transconductance self-aligned gate-last surface channel In 0.53 Ga 0.47 As MOSFET

In this paper we present a 55 nm gate length In0.53Ga0.47As MOSFET with extrinsic transconductance of 1.9 mS/µm and on-resistance of 199 Ωµm. The self-aligned MOSFET is formed using metalorganic chemical vapor deposition regrowth of highly doped source and drain access regions. The fabricated 140 nm gate length devices shows a low subthreshold swing of 79 mV/decade, which is attributed to the described low temperature gate-last process scheme.

RF Characterization of Vertical InAs Nanowire Wrap-Gate Transistors Integrated on Si Substrates

We present dc and RF characterization of InAs nanowire field-effect transistors (FETs) heterogeneously integrated on Si substrates in a geometry suitable for circuit applications. The FET consists of an array of 182 vertical InAs nanowires with about 6-nm HfO2 high-k gate dielectric and a wrap-gate length of 250 nm. The transistor has a transconductance of 155 mS/mm and an on-current of 550 mA/mm at a gate voltage of 1.5 V and a drain voltage of 1 V. S-parameter measurements yield an extrinsic cutoff frequency of 9.3 GHz and a extrinsic maximum oscillation frequency of 14.3 GHz.

Slot-Coupled Millimeter-Wave Dielectric Resonator Antenna for High-Efficiency Monolithic Integration

A readily mass-producible, flip-chip assembled, and slot-coupled III-V compound semiconductor dielectric resonator antenna operating in the millimeter-wave spectrum has been fabricated and characterized. The antenna has a 6.1% relative bandwidth, deduced from its 10 dB return loss over 58.8–62.5 GHz, located around the resonance at 60.5 GHz. Gating in the delay-domain alleviated the analysis of the complex response from the measured structure. The radiation efficiency is better than

20 GHz Wavelet Generator Using a Gated Tunnel Diode

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Coherent V-Band Pulse Generator for Impulse Radio BPSK

dB in simulations fed from the on-chip coupling-structure, but reduced by 3.7 dB insertion loss through the measurement assembly feed. Antenna gain measurements show distortion in relation to the simulated pattern, which has a maximum gain of 6 dBi, mainly caused by interference from the electrically large connector used in the assembly. Mode degeneration in the utilized quadratic-footprint resonator was not seen to influence the performance of the antenna. The antenna is intended for on-chip integration and the fabrication technology allows scaling of the operation frequency over the complete millimeter-wave spectrum.

Bias Stabilization of Negative Differential Conductance Oscillators Operated in Pulsed Mode

We demonstrate the use of a GaAs-AlGaAs gated tunnel diode (GTD) in an ultra-wideband (UWB) wavelet generator. An inductor is integrated to form an oscillator circuit, which is driven by the negative differential conductance property of a GTD. It is demonstrated that as the gate tunes the magnitude of the output conductance, the oscillator may be switched on and off, creating short RF pulses. The shortest pulses generated are 500 ps long, the highest output power for the free running oscillator is -4.1 dBm, and the highest oscillation frequency is 22 GHz. Analytical expressions based on the van der Pol equation describing the pulse length and amplitude are presented. This technique is applicable for high frequency impulse radio UWB implementations.

High-Frequency Performance of Self-Aligned Gate-Last Surface Channel MOSFET

A coherent pulse generator for implementation in an impulse radio system is presented. It accurately transforms a 12.5 GHz square wave input signal to 33 ps long 60 GHz pulses. The wavelets are generated through direct conversion from baseband to 60 GHz by switching a negative differential conductance oscillator on and off. The slope of the input signal determines the phase, which is either I + or I -. The generator is feasible for use in coherent radio systems since the method shows consistent startup and decay of the generated wavelets. The coherence between the input baseband signal and wavelet output signal is demonstrated in an eye diagram with rms jitter <; 1.3 ps. The oscillator is implemented with a gated resonant tunneling diode where the input level also can be used to tune the center frequency of the wavelets.

High-Frequency Performance of Self-Aligned Gate-Last Surface Channel In0.53Ga0.47As MOSFET

The paper reports on the bias stabilization of a 60-GHz resonant-tunneling diode (RTD)-based oscillator operated in pulsed mode. The oscillator contains an on-chip stabilizing capacitor, enabling the minimum dc consumption possible for such an RTD oscillator to be obtained, since all of the dc current is consumed by the active device. This is achieved without imposing restraints on the output power or introducing parasitic oscillations in the bias network. The oscillator that was constructed produces short 75-ps wavelets at 60 GHz, at an energy consumption of 1.3 pJ, during generation of a pulse. Experimental, simulated, and analytical results are presented for demonstrating how this mode of operation can be utilized in negative differential conductance oscillators.

60 GHz ultra-wideband impulse radio transmitter

We have developed a self-aligned L_g = 55 nm In_0.53Ga_0.47As MOSFET incorporating metal-organic chemical vapor deposition regrown n⁺⁺ In_0.53Ga_0.47As source and drain regions, which enables a record low on-resistance of 199 Ωμm. The regrowth process includes an InP support layer, which is later removed selectively to the n⁺⁺ contact layer. This process forms a high-frequency compatible device using a low-complexity fabrication scheme. We report on high-frequency measurements showing f_max of 292 GHz and f_t of 244 GHz. These results are accompanied by modeling of the device, which accounts for the frequency response of gate oxide border traps and impact ionization phenomenon found in narrow band gap FETs. The device also shows a high drive current of 2.0 mA/μm and a high extrinsic transconductance of 1.9 mS/μm. These excellent properties are attributed to the use of a gate-last process, which does not include high temperature or dry-etch processes.