Effect of impact ionization in scaled pHEMTs

The effect of impact ionization on pseudomorphic high electron mobility transistors is studied using Monte Carlo simulations when these devices are scaled into deep decanano dimensions. The scaling of devices with gate lengths of 120, 90, 70, 50 and 30 nm has been performed in both lateral and vertical directions. The impact ionization is treated as an additional scattering mechanism in the Monte Carlo module. The critical drain voltage, at which device characteristics begin to indicate breakdown, decreases as the gate voltage is lowered. Similarly, the breakdown drain voltage is also found to decrease during the scaling process

RF analysis of aggressively scaled pHEMTs

No abstract avaliable

Fabrication of submicron planar Gunn diode

We present, for the first time, the fabrication process for a submicron planar Gunn diode in In<sub>0.53</sub>Ga<sub>0.47</sub>As on an InP substrate operating at 265 GHz. A novel two stage lift off method has been developed to achieve a submicron gaps between contacts down to 135 nm with widths up to 120 μm

Semiconductor device for generating an oscillating voltage

A semiconductor device which displays an oscillating voltage due to the creation of charge domains which includes a plurality of semiconductor layers and at least two electrodes spaced from one another in the direction of the layers, an upper of which has a composition and/or dimensions predetermined so that a charge therein balances a depletion from a surface charge of the upper layer on application of a potential difference across said electrodes. The electrodes may be in contact solely with the upper layer. A method of manufacturing the device is also provided

Ultrafast harmonic mode-locking of monolithic compound-cavity laser diodes incorporating photonic-bandgap reflectors

We present the first demonstration of reproducible harmonic mode-locked operation from a novel design of monolithic semiconductor laser comprising a compound cavity formed by a 1-D photonic-bandgap (PBG) mirror. Mode-locking (ML) is achieved at a harmonic of the fundamental round-trip frequency with pulse repetition rates from 131 GHz up to a record high frequency of 2.1 THz. The devices are fabricated from GaAs-Al-GaAs material emitting at a wavelength of 860 nm and incorporate two gain sections with an etched PBG reflector between them, and a saturable absorber section. Autocorrelation studies are reported which allow the device behavior for different ML frequencies, compound cavity ratios, and type and number of intra-cavity reflectors to be analyzed. The highly reflective PBG microstructures are shown to be essential for subharmonic-free ML operation of the high-frequency devices. We have also demonstrated that the single PBG reflector can be replaced by two separate features with lower optical loss. These lasers may find applications in terahertz; imaging, medicine, ultrafast optical links, and atmospheric sensing

Terahertz Microstrip Elevated Stack Antenna Technology on GaN-on-Low Resistivity Silicon Substrates for TMIC

In this paper we demonstrate a THz microstrip stack antenna on GaN-on-low resistivity silicon substrates (ρ < 40 Ω.cm). To reduce losses caused by the substrate and to enhance performance of the integrated antenna at THz frequencies, the driven patch is shielded by silicon nitride and gold in addition to a layer of benzocyclobutene (BCB). A second circular patch is elevated in air using gold posts, making this design a stack configuration. The demonstrated antenna shows a measured resonance frequency in agreement with the modeling at 0.27 THz and a measured S11 as low as −18 dB was obtained. A directivity, gain and radiation efficiency of 8.3 dB, 3.4 dB, and 32% respectively was exhibited from the 3D EM model. To the authors' knowledge, this is the first demonstrated THz integrated microstrip stack antenna for TMIC (THz Monolithic Integrated Circuits) technology; the developed technology is suitable for high performance III-V material on low resistivity/high dielectric substrates

Monte Carlo simulations of high-performance implant free In_0.3Ga_0.7 nano-MOSFETs for low-power CMOS applications

No abstract available

Self-aligned 0.12mm T-gate In.53Ga.47As/In.52Al.48As HEMT Technology Utilising a Non Annealed Ohmic Contact Strategy

An InGaAs/InAlAs based HEMT structure, lattice matched to an InP substrate, is presented in which drive current and transconductance has been optimized through a double-delta doping strategy. Together with an increase in channel carrier density, this allows the use of a non-annealed ohmic contact process. HEMT devices with 120 nm standard and self-aligned T-gates were fabricated using the non-annealed ohmic process. At DC, self-aligned and standard devices exhibited transconductances of up to 1480 and 1100 mS/mm respectively, while both demonstrated current densities in the range 800 mA/mm. At RF, a cutoff frequency f/sub T/ of 190 GHz was extracted for the self-aligned device. The DC characteristics of the standard devices were then calibrated and modelled using a compound semiconductor Monte Carlo device simulator. MC simulations provide insight into transport within the channel and illustrate benefits over a single delta doped structure