InP/Al2O3n-channel inversion-mode m.i.s.f.e.t.s using sulphur-diffused source and drain

InP metal-insulator-semiconductor field-effect transistors (m.i.s.f.e.t.s) have been fabricated using c.v.d. Al2O3 as the gate insulator and the sulphur-diffusion process for source and drain. The n-channel inversion-mode device exhibits normally off behaviour. A maximum d.c. transconductance gm of 10 mS (87 mS/mm of gate width) has been obtained.     

Avalanche noise in GaAs m.e.s.f.e.t.s

Instabilities in the d.c. characteristics of GaAs m.e.s.f.e.t.s for drain to source voltages greater than 4 V. believed to be due to reloading of traps in the interface between active layer and bulk material, or gunn-domain formation, seem to have their origin in avalanche breakdown of the back diode under the drain contact. Microplasma switching, vertical to the active layer, strongly modulates the drain current producing large broadband noise power.     

Short-channel polysilicon-gate m.o.s.f.e.t.s fabricated by c.w. argon laser annealing of arsenic-implanted source and drain

Short-channel polysilicon-gate n-channel m.o.s.f.e.t.s have been successfully fabricated using c.w. argon laser annealing of arsenic-implanted source and drain. The turn-on voltage is higher for the laser annealed devices than for those annealed thermally, which were processed identically except for the source and drain annealing. Laser annealing also reduced the n+-layer sheet resistance to about half that of the thermally annealed n+ regions.     

Conversion gain of m.e.s.f.e.t. drain mixers

A theoretical analysis of the gain properties of m.e.s.f.e.t. drain mixers is presented. The m.e.s.f.e.t. model includes the nonlinearity of both the transconductance and the drain resistance. For a special case, a simple analytical expression for the gain is given. Numerical results for a typical example are briefly presented as an illustration.     

Remediable and nonremediable causes of parasitic elements in InP m.e.s.f.e.t.s

Two-dimensional analyses of InP and GaAs m.e.s.f.e.t. structures are used to qualitatively explain relative magnitudes of parasitic element values observed in experimental InP m.e.s.f.e.t.s. Large drain-gate capacitance observed in InP is attributed mainly to substrate conduction, whereas large drain conductance at certain drain biases in InP may be unavoidable due to large velocity dropback and large high-field diffusion in this material. Low Schottky-barrier height and substrate conduction also increase gD     

Simple I/V model for short-channel i.g.f.e.t.s in the triode region

The standard 1-dimensional model for an i.g.f.e.t. in the triode region predicts values of the drain current ID that fall increasingly below experimental values as the channel is shortened or as the drain voltage VD is increased. However, a strictly 2-dimensional treatment results in prohibitive computation. A model is described that takes into account fringing fields at each end of the channel and which requires a relatively simple numerical solution of two nonlinear equations. Experiments on p channel i.g.f.e.t.s with gate lengths of 1.6 to 7.8 ?m show that this model predicts I/V characteristics much better than does the standard 1-dimensional model which includes the bulk charge.     

Flip-chip mounted GaAs power f.e.t. with improved performance in X- to Ku-band

A GaAs power m.e.s.f.e.t. with a new structure has been developed, which allows extremely reduced source inductances and minimised thermal resistance. In the structure, the chip, with metal posts plated on the source, drain and gate pads, is connected directly to the package with no wire. The best results obtained were 2.5 W at 15 GHz and 4.1 W at 12 GHz.     

New estimate of the minimum noise figure of a m.e.s.f.e.t.

New estimates of the drain and gate noise multiplication parameters, the correlation coefficient and the minimum noise figure for a m.e.s.f.e.t. are advanced. For an uncooled GaAs m.e.s.f.e.t. having a 1 ?m gate length, a minimum possible noise figure of 1 dB at 10 GHz is predicted. InP is only marginally better.     

Analysis of field distributions in a GaAs m.e.s.f.e.t. at large drain voltages

Electric-field distributions and carrier-density distributions in a GaAs m.e.s.f.e.t. at large drain voltages are investigated with a new analytical model, which takes account of the electron-drift-velocity saturation with negative differential mobility and the extension of a depletion layer towards the drain electrode.     

Dual-gate m.e.s.f.e.t. self-oscillating X-band mixers

GaAs dual-gate m.e.s.f.e.t.s have been successfully used as self-oscillating down-convertors in X-band. A single device replaces the preamplifier, mixer and local oscillator. The best conversion gain achieved by mixing from 10 GHz down to 1 GHz was 12 dB. The input (gate 1) to output (drain) port isolation amounted to 16 dB. Slug-tuner and `disc?-resonator circuits were tested and showed comparable gain and noise performance. Best d.s.b. noise figures of 5.5 dB could be realised at an i.f. of 1 GHz with an associated conversion gain of 4 dB.     

Tungsten/gold gate GaAs microwave f.e.t.

Preliminary results on the performance of a W/Au gate GaAs f.e.t. having T-type gate cross-section are reported. The Au overhang on the W gate can be used to self-align the source and the drain with respect to the gate, which can be used to achieve submicrometre gate dimensions rather easily. An f.e.t. with 0.7 ?m gate length and 140 ?m gate periphery exhibited a measured maximum available gain (m.a.g.) of 14 dB at 8 GHz, Experiments on the W Schottky diodes indicate that the leakage current, instead of degrading, is actually reduced by annealing at high temperature in a H2 atmosphere for 10 min.     

Enhancement-mode GaAs m.o.s.f.e.t. on semi-insulating substrate using a self-aligned gate technique

A self-aligned gate notched channel GaAs m.o.s.f.e.t. structure on semi-insulating substrate is presented. Device operation is mainly in enhancement mode. The transconductance is comparable to enhancement-mode m.e.s.f.e.t.s, j.f.e.t.s and s.i.g.f.e.t.s; however, the output-current capability is essentially increased.     

Medium-power GaAs field-effect transistors

Results on medium-power GaAs m.e.s.f.e.t.s. are described. Output powers as high as 300 mW at 9 GHz at 1 dB gain compression with a linear gain of 5.2 dB and drain efficiency of 30% have been obtained with single-cell m.e.s.f.e.t.s. At 4 GHz, a power output of 665 mW at 1 dB gain compression, a linear gain of 8 dB and a drain efficiency of 44.5% were realised with a 3-cell m.e.s.f.e.t. Two-tone intermodulation characteristics at 4 GHz are also described. A major innovation has been the use of a high-resistivity chromium-doped epitaxial GaAs buffer layer to isolate the device active region from the bulk-grown substrate.     

n-channel m.i.s.f.e.t.s in epitaxial HgCdTe/CdTe

M.I.S.F.E.T.s have been fabricated in HgCdTe epitaxially grown on CdTe substrates. These planar n-channel f.e.t.s use ZnS as the insulator and Be ion implantation for the source and drain regions. Surface mobilities of 7×103 cm3/Vs at 77 K are reported.     

GaAs power f.e.t.s with semi-insulated gates

GaAs semi-insulated-gate f.e.t.s (s.i.g.f.e.t.s) have been fabricated by Ar+ bombardment in the gate region. The d c. characteristics and microwave performance are compared with those of conventional power m.e.s.f.e.t.s fabricated from the same slice. Up to 2.9W output power with 4dB gain has been obtained from s.i.g.f.e.t. devices at 8 GHz.     

Gigahertz p-channel enhancement silicon m.o.s.f.e.t. with nonoverlapping gate

The technological and electrical parameters of p-channel enhancement silicon m.o.s.f.e.t.s with recessed gates are presented and compared with conventional structures fabricated in a similar manner. In the instance of the nonoverlapping gate the gain-bandwidth product is increased by a factor of about 3. The maximum frequency, as obtained by extrapolation of measurements up to 1 GHz, is f/SUB max//spl ap/3 GHz. If the depletion region of the drain contact is too short to overlap with the gate field, the static characteristics follow a space-charge-limited current-voltage relation. When higher source-drain voltages are applied the normal enhancement-type behavior results but with reverse transconductance y/SUB r/ strongly reduced (by a factor of 8-12 at 1 GHz). A higher circuit stability is obtainable, whereas the parameters y/SUB i/,y/SUB 0/, and y/SUB f/ are only slightly influenced.     

Silicon-on-sapphire m.o.s.f.e.t.s fabricated by back-surface laser-anneal technology

Self-aligned aluminium-gate silicon-on sapphire (s.o.s.) m.o.s.f.e.t.s have been fabricated by applying laser-anneal technology from the back surface for activation of the ion-implanted channel layer. The threshold voltage and surface electron mobility were similar to the conventional silicon-gate m.o.s.f.e.t.s, but the low resistivity of gate and interconnection electrodes using aluminium is advantageous for high switching speed m.o.s. l.s.i.     

Conditions for optimum noise performance in l.f. amplifiers employing junction f.e.t.s

Increasing the drain current of an f.e.t. can result in an improvement of the noise performance at medium frequencies, but, owing to changes in the noise spectrum of the device, a deterioration of the low-frequency noise performance can result. Measurements in the frequency range 1 Hz?1 kHz on some low-noise samples of f.e.t.s show that the drain current is not critical up to a limit, but, above this limit, the noise performance below 10 Hz deteriorates rapidly.     

wo-dimensional finite element simulation of semiconductor devices

Semiconductor-device modelling in two dimensions by the finite-element method is described. Results of application to a GaAs m.e.s.f.e.t. are given. Negative differential drain conductance is observed.     

Test of the thermal-noise hypothesis in m.o.s.f.e.t.s

Evidence is given that, for m.o.s.f.e.t.s, another source o noise besides thermal noise must be operating in the conducting channel.