Gigahertz Operation of a-IGZO Schottky Diodes

Abstract

We present vertical Schottky diodes based on amorphous IGZO with an unprecedented cutoff frequency of 1.8 GHz at 0 V bias. These diodes have a rectification ratio of up to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> at ±1 V and a current density of 800 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at +1 V. The diodes' high performance is achieved by understanding and modeling of the two contacts, a Schottky contact using Pd at the bottom and an ohmic contact formed at the top. In particular, the choice of the latter top contact combined with an optimized IGZO layer thickness proves to be crucial: we show how the semiconductor layer thickness and the nature of the top metal modify the doping concentration profile of the IGZO film, which we fully measure and characterize, and how that affects the performance and optimization of the diodes. We measure our diodes in rectifiers, which operate up to 1.1 GHz. Finally, we show that these rectifiers can be fully modeled in SPICE using diode parameters extracted from electrical measurements.