III-nitride transistors with capacitively coupled contacts

Abstract

Al Ga N ∕ Ga N heterostructure field-effect transistor design using capacitively coupled contacts (C3HFET) is presented. Insulated-gate [C3 metal-oxide-semiconductor HFET (C3MOSHFET)] has also been realized. The capacitively coupled source, gate, and drain of C3 device do not require annealed Ohmic contacts and can be fabricated using gate alignment-free technology. For typical AlGaN∕GaN heterostructures, the equivalent contact resistance of C3 transistors is below 0.6Ωmm. In rf-control applications, the C3HFET and especially the C3MOSHFET have much higher operating rf powers as compared to HFETs. C3 design is instrumental for studying the two-dimensional electron gas transport in other wide band gap heterostructures such as AlN∕GaN, diamond, etc., where Ohmic contact fabrication is difficult.

Lowering contact resistance of graphene FETs with capacitive extension of ohmic contacts for enhanced RF performance

“…The results from simulation and analytical calculation were in a very good agreement to validate our simulation technique used to estimate the impedance of a capacitor-like structure. Once our simulation technique for estimating capacitive impedance was verified, we verified our C3 simulation method by successfully simulating a III-N RF TLM structure reported in [21].…”

“…The C3 impedance can be calculated analytically by considering it as a RC transmission line [21]. In C3 GFET, the contact metal and Graphene channel with in-between dielectric material form a RC transmission line whose propagation constant γ and characteristics impedance Z0 can be expressed as:…”

Novel RF devices with multiple capacitively-coupled electrodes

“…For operating frequencies in the gigahertz range, III-N based RF switches can be fabricated using capacitively-coupled contacts (C 3 ) [4,5]. The C 3 technology can use robust, selfaligned metallization process that does not require contact annealing.…”

Advanced Graphene Microelectronic Devices

“…The C3 can be considered as a RC transmission line and its impedance can be analytically calculated [38]. If a C3 is placed on top of Gate dielectric, the contact metal and Graphene channel with in-between dielectric material form a RC transmission line.…”

“…For further verification, we successfully regenerated the experimental data for III-N RF TLM structures reported in [38]. To estimate the impedance of the capacitance formed between a C3 and Graphene channel with Gate dielectric in-between, we simulated a RF TLM structure on Graphene having two C3s with various in-between distances.…”