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Hybrid MESFET MOSFET Logic Circuit

IP.com Disclosure Number: IPCOM000048264D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Fang, FF: AUTHOR [+2]

Abstract

While MESFETs (metal silicon field effect transistors) are known for their simplicity in fabrication and capability for low power high performance operation, the low voltage enhancement type of MESFET (E/MESFET) switching device requires rather critical load device characteristics to form an elemental logic inverter. An improvement is provided by incorporating an electrically adjustable load device-buried channel or surface channel depletion MOSFET (D/MOSFET) as an integral part of the inverter.

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Hybrid MESFET MOSFET Logic Circuit

While MESFETs (metal silicon field effect transistors) are known for their simplicity in fabrication and capability for low power high performance operation, the low voltage enhancement type of MESFET (E/MESFET) switching device requires rather critical load device characteristics to form an elemental logic inverter. An improvement is provided by incorporating an electrically adjustable load device-buried channel or surface channel depletion MOSFET (D/MOSFET) as an integral part of the inverter.

The improvement structure is shown in Fig. 1, and the electrical performance curves are shown in Fig. 2. In Fig. 1, a schematic n channel E/MESFET-D/buried channel MOSFET (D/BMOSFET) inverter structure is shown in which channel doping profiles are identical for both FETs. Source and drain regions also have identical structural and metallurgical configurations. The only difference is the gate structure where Schottky and MOS junctions are employed for the E/MESFET and D/BMOSFET, respectively. In the device of Fig. 1, in the absence of oxide charge and work function difference between n-Si and gate metal, the D/BMOSFET has threshold voltage V(th) equals -4pi q delta(ox) N(d) divided by k(ox) in cgs units, where delta(ox) is the oxide thickness, N(d) is the areal donor density of the channel, and K(ox) is the dielectric constant.

For typical E/MESFET, N(d) is approximately equal to 10/12/ per sq cm. Thus, for delta(ox) equals 200 angstroms,...