n-channel inversion-mode InP m.i.s.f.e.t.

Capacitance/voltage and m.i.s.f.e.t. inversion-mode f.e.t. data are reported for p-type InP. It is shown that the surface of this material appears to be inverted at zero gate bias and that good inversion-mode (normally-off) device behaviour is possible.     

Microwave gain from an n-channel enhancement-mode InP m.i.s.f.e.t.

A power gain of 14 dB at 1 GHz has been demonstrated in an enhancement-mode m.i.s.f.e.t. constructed on an Fe-doped semi-insulating InP substrate. The same device also exhibits well behaved gain characteristics at low frequencies.     

n-channel formation on semi-insulating InP surface by m.i.s.f.e.t.

InP m.i.s.f.e.t.s using Fe-doped semi-insulating material surface have been fabricated. The devices, composed of sulphur-diffused n-type source and drain and c.v.d. Al2O3 gate insulator, exhibited n-channel normally-off behaviour and a source drain capacitance two orders of magnitude smaller than that of p-InP m.i.s.f.e.t.s with the same dimensions.     

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.     

New n-channel m.o.s.f.e.t.s

By using plasma c.v.d. and lift-off, an n-channel m.o.s.f.e.t. with effective channel length of 0.4 ?m has been fabricated. Its main fabrication processes and obtained electrical characteristics are described.     

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.     

Substrate dependence of InP m.e.s.f.e.t. performance

There is evidence to suggest that Fe outdiffuses, during the growth, into the epitaxial films prepared by vapour-phase epitaxy at 650°C. Field-effect transistors on Fe-doped material show substantial looping that was absent on Cr-doped material and exhibit about 2 dB worse noise figure at about 7 GHz. Experiments with low 1015 S-doped InP grown on Sn-, Cr- and Fe-doped substates indicate that such outdiffusion is typically about 5 ?m. Saturation velocity levels in the m.e.s.f.e.t. channel are about 1.7 × 107 cm/s and 1.3 × 107 cm/s, associated with Cr and Fe doped substrates, respectively.     

Enhancement-mode ion-implanted InP f.e.t.s

Planar enhancement-mode InP f.e.t.s have been fabricated through the use of ion implantation and subsequent electron-beam lithography. Noise figures of 3.2 and 2.6 dB were achieved at 8 GHz with associated gains of 6.4 and 4.7 dB, respectively.     

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     

Multi/demultiplexing in Gbit/s range using dual gate GaAs m.e.s.f.e.t.s

Multiplexing from 1 to 2 Gbit/s and corresponding demultiplexing from 2 to 1 Gbit/s including clock regeneration and pulse width reduction has been performed using dual gate GaAs m.e.s.f.e.t.s. Circuits and time behaviour of input, clock and output signals are shown.     

Low-noise GaAs m.e.s.f.e.t.s

GaAs m.e.s.f.e.t.s with optimum noise figures of 1.6 dB at 6 GHz have been fabricated by projection photolithography. An equation has been developed for the calculation of optimum noise figure which gives good agreement between calculated and measured values.     

Femtojoule logic circuit using normally-off GaAs m.e.s.f.e.t.s

Experimental results are reported on the speed/power performance of normally-off-type GaAs-m.e.s.f.e.t. logic circuits, using an integrated 15-stage ring oscillator as a test circuit. A power consumption as low as 1-5 ?W, corresponding to a power-delay product of 1.6 fJ, was obtained. Conversely, a propagation delay time of 650 ps was measured for a power consumption of 20 ?W per gate.     

GaAs gigabit logic circuits using normally-off m.e.s.f.e.t.s

Normally-off GaAs m.e.s.f.e.t. logic circuits fabricated by electron beam lithography have exhibited excellent high speed switching characteristics. The highest switching speed evaluated from a 15-stage ring oscillator is 30 ps per gate with a power dissipation of 1.9 mW. Binary frequency dividers have been fabricated with D-type flip-flops operating up to 3 GHz. A divide-by-eight counter has also operated at 2.5 GHz.     

Microwave power amplification with InP f.e.t.s

InP f.e.t.s were fabricated from v.p.e. layers, with an Al gate of 1.5 ?m × 308 ?m. The power output at 9 GHz, with 4 dB gain, was 1.15 W/mm gate width. This result is believed to be higher than the best published results obtained with equivalent GaAs f.e.t. structures.     

Bit synchronisation in Gbit/s range using dual gate GaAs m.e.s.f.e.t.s

Bit synchronisation at 1 and 2 Gbit/s including pulse width reduction is achieved using dual gate GaAs m.e.s.f.e.t.s. Circuits and time behaviour of input-, clock- and output signals are shown.     

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.     

High-speed 1 ?m GaAs m.e.s.f.e.t.

By minimising parasitic series resistances, a GaAs m.e.s.f.e.t. with 1 ?m gate length was fabricated, possessing the highest known r.f. power gain, measured up to 18 GHz, for GaAs m.e.s.f.e.t.s.     

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.     

Performance of GaAs power m.e.s.f.e.t.s

Power performance results at 4 GHz are summarised for GaAs m.e.s.f.e.t.s ranging in size from 4 to 16 mm gate periphery. A double-chip 16 mm unit operated at 24 V source-drain bias produced 13.5 W with 3 dB gain and 10.7 W with 8.1 dB gain. Although lack of perfect power and gain scaling is observed, the degradation in output power of the 16 mm devices was only 1 dB compared to the smaller devices.     

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.