Low-frequency noise behavior of 0.15-μm gate-lengthlattice-matched and lattice-mismatched MODFETs on InP substrates

Experimental data are presented on equivalent gate noise voltage from 1 to 10⁵ Hz obtained from lattice-matched and strained InGaAs quantum-well modulation-doped field effect transistors (MODFETs). In both types of devices excess generation-recombination (g-r) noise is observed at or below 100 Hz above an `apparent' background 1/f noise with spectral intensity ranging from 0.5×10^-17 to 2×10^-17 V²-Hz^-1-cm² at 1 Hz. These results are comparable to those reported by S.M.J. Liu et al. (1986) for the pseudomorphic MODFETs     

Determination of source and drain series resistances of ultra-shortgate-length MODFETs

A practical method to evaluate the parasitic source and drain series resistances of modulation-doped FETs is presented. The method is based on a modified gate-probe technique that uses the gate current crowding phenomenon. It is suitable for complex heterostructure devices since the carrier transport mechanism and physical structure properties around the gate region need not conform to ideal models     

Optimization of gate-to-drain separation in submicron gate-lengthmodulation doped FET's for maximum power gain performance

This paper analyzes the effects of the separation between the gate and the drain electrodes on the high-frequency performance limitations of heterostructure MODFET's. Based on the effective gate-length and carrier velocity saturation concepts first the key small-signal equivalent network model parameters of the MODFET are calculated. The concept of open-circuit voltage gain, defined as the transconductance to output conductance ratio (g_m/g_o), has been exploited to determine the output conductance with a knowledge of the static electric field and potential at the edge of the gate on the drain side. By treating the c_oμ_n product as a function of the gate voltage, the drain current-voltage and transconductance characteristics have been effectively modeled for practical devices. By combining the effects of the intrinsic and parasitic equivalent network parameters this paper has determined the dependence of the g_m/g_o ratio, the gate capacitance to the feedback capacitance ratio, the unity current gain frequency (f_r) and the maximum frequency of oscillations (f _max) on the gate-to-drain separation (L_gd). MODFET's based on InAlAs/InGaAs heterostructures lattice-matched to InP substrate with gate-length values of 0.25 μm, 0.15 μm and 0.1 μm are considered for analyses. The optimum values of L_gd calculated are 600 Å, 420 Å, and 340 Å for the corresponding maximum f_max-values of 250, 370, and 480 GHz, respectively