The super-Schottky diode at 30 GHz

Abstract

The super-Schottky diode mixer is extended to a frequency of 30 GHz using a barrier modification technique to alter the metal-semiconductor interface. Control of the metal-semiconductor barrier, developed here for the super-Schottky, introduces a new technological tool for tailoring the properties of junction devices. Reducing the barrier height of Pb contacts to p-GaAs increases the conductivity of the junction, allowing a reduction in area to achieve the diode impedance required for matching. This area reduction decreases the shunt capacitance, which is the chief parasitic element of the super-Schottky diode at high frequencies. A second technique available for extending such devices to higher frequencies is the electrolithographically produced multiple contact array structure. This multiple contact concept requires exceptional uniformity in deposition of the metal contacts. Such uniformity is unattainable with conventional electroplating. A new high-field pulsed-plating technique has recently been developed to yield Schottky contact arrays with uniformly theoretical spreading resistances at diameters as small as 1200 A. Arrays with 100 individual diode contacts are now being routinely produced. The area reduction due to barrier height lowering, however, has produced individual super-Schottky diodes whose capacitance is decreased by over an order of magnitude. This reduction in capacitance implies that single mixer diodes will achieve a conversion loss of 7 dB, a mixer noise temperature of 6 K, and a video NEP of 5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-16</sup> W/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> at 30 GHz.