USA As Represented by Secretary of the Navy

US Government As Represented by the Secretary of the Army

H Alfred Hung

Pankaj B Shah

A varactor comprising two Schottky diodes, each diode comprising a substrate and a plurality of layers formed on the substrate including at least one GaN layer and at least one semi-insulating material layer formed of a material with an energy gap greater than 3.5 and free carrier mobility less than 300 cm/V-s; the Schottky diodes having cathodes adapted to be connected to an AC voltage input and being configured so that as the AC voltage applied to the cathodes increases the capacitance decreases nonlinearly, the nonlinear transition from high capacitance to low capacitance being adjustable by utilizing the intrinsic carrier concentration of the semi-insulating layer to obtain an optimal nonlinear transition for the predetermined AC voltage applied to the cathodes. A method of making a varactor comprising computer modeling to produce capacitance-voltage curves, modifying at least one semi-insulating region, and modeling power input/output efficiency for a predetermined input signal.

Group III nitride semiconductor frequency multiplier

A preferred method of optimizing a Ga-nitride device material structure for a frequency multiplication device comprises:

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Bethesda, MD, United States of America

H Alfred Hung