Two-dimensional Field-effect Transistors Research Articles

Low frequency noise in two-dimensional metal-semiconductor field effect transistor

Low frequency noise in the two-dimensional metal-semiconductor field effect transistor (2D-MESFET) is reported. It is shown that the noise level S is rather small. At room temperature the value of Hooge constant α was about 2×10−5 for frequency f=20 Hz. The frequency dependence of the relative spectral density of current fluctuations SI/I2 at 300 K was close to S∼1/f0.6 in the frequency range 20 Hz–20 kHz. Two local maxima were observed in the temperature dependence of S in the ranges 100–180 K and 200–300 K.

Two-dimensional metal-semiconductor field effect transistor for ultra low power circuit applications

We describe a novel 2-dimensional metal-semiconductor field effect transistor (2-D MESFET) in which opposing Schottky side gates formed on the sidewall of a modulation-doped AlGaAs-InGaAs heterostructure modulate the channel width and the drain current. The drain current ranged from 0 to 210 μA and the maximum measured transconductance was 212 μS (212 mS/mm) at room temperature for a 1×1 micron channel. The threshold voltage was -0.45 V and the subthreshold ideality factor was 1.30. The estimated gate capacitance was 0.8 fF/μm, or about half the equivalent capacitance of conventional HFET's. The cutoff frequency f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> was estimated to be 21 GHz. The narrow channel effect, which limits the minimum power consumption in conventional FET's, is practically eliminated in this device.

High electron density and mobility in single and double planar doped InGaAs/InAlAs heterojunctions on InP

We present results of a growth study concerning the electrical properties of lattice matched InAlGa/InGaAs single planar doped (SPD) and double planar doped (DPD) heterostructures grown on InP by molecular beam epitaxy (MBE). It is shown that room temperature electron mobilities (μ H) as high as 11000 cm 2/V·s at high sheet densities of 2.8x10 12 cm −2 can be obtained by optimizing the growth temperatures of each material in the SPD structure. High performance two-dimensional electron gas field effect transistors (TEGFET's) are demonstrated, with transconductances as high as 420 mS/mm at 1 μm gatelength and ƒ T's of 46 GHz at 0.7 μm gatelength. The DPD heterostructures further boost the n s values up to 6.2x10 12 cm -2 at μ H (300 K) = 6000 cm 2/ Vctdot; s.

Analysis of charge control in pseudomorphic two-dimensional electron gas field-effect transistors

An exact model for charge control in two-dimensional field-effect transistors (2DEGFETs) is discussed. The model is based on a first-principles theory, in which self-consistent quantum two-dimensional electron subbands and numerical solutions of Poisson's equation for band bending, space charge, and three-dimensional holes are included. The charge control in InGaAs/AlGaAs pseudomorphic 2DEGFETs is analyzed and compared with that in the GaAs/AlGaAs conventional 2DEGFET. It is shown that a quantum-well channel in the pseudomorphic 2DEGFET can achieve high carrier confinement as well as high carrier concentration. From the calculated gate capacitance-voltage behavior, a simple estimation for the device performance is obtained. The results indicate that the pseudomorphic 2DEGFET with a large conduction band discontinuity at the channel interface can improve transconductance-gate voltage characteristics, and thus maximum transconductance, and the cutoff frequency-gate voltage characteristics. >

Noise modeling in submicrometer-gate two-dimensional electron-gas field-effect transistors

Noise modeling in TEGFET's which provides good results in agreement with the experimental findings is presented. The influence of the main technological parameters on the noise figure and associated gain is given for operating frequencies up to 60 GHz. A comparison between TEGFET's and MESFET's is carried out. A new method for calculating the noise and gain performances of FET's is then proposed.

Abrupt OMVPE grown GaAs/GaAlAs heterojunctions

In this paper, we describe the growth of abrupt heterojunctions and very thin GaAs and GaAlAs layers for use in quantum well lasers or TEGFET (two-dimensional electron-gas field effect transistors) structures. SIMS measurements have been performed which confirm that the growth rate measured for thick layers (1 to 10 μm) can be used to estimate the thickness of very thin layers (<100 Å) with a good accuracy. Luminescence data from GaAlAs/GaAs/GaAlAs quantum wells shows that there is probably some random compositional fluctuation in the GaAlAs quantum well barrier layers which leads to a broadening of the luminescence peak and a shift to lower energy. These quantum wells form the active layer of separate confinement heterostructure (SCH) and graded refractive index (GRIN) SCH quantum well laser structures. We will review the results of our study of these lasers explaining the separate roles of the GRIN and quantum well. New results will be given showing how the value of T 0 can be improved by increasing, the number of quantum wells in the active layer.