# Wafer-scale radio frequency ZnO Schottky diodes and arithmetic circuits

## TL;DR

This paper presents a scalable method to create fast zinc oxide diodes and integrate them into arithmetic circuits for next-generation telecommunications.

## Contribution

A modified adhesion lithography method for wafer-scale fabrication of high-performance ZnO Schottky diodes and logic circuits.

## Key findings

- Planar ZnO diodes achieved high current rectification and a cut-off frequency over 25 GHz.
- Monolithic integration of diodes enabled functional 2-bit Half-Adder circuits on 4-inch wafers.
- The method offers a scalable alternative for large-area, high-speed electronics.

## Abstract

Modern telecommunication technologies, such as the 5G and upcoming 6G networks, rely on devices operating in the radio frequency (RF) spectrum of 0.3–90 GHz and 7–300 GHz, respectively. To meet these demanding frequency requirements, new manufacturing methods and device architectures are gaining increasing attention. However, achieving scalable manufacturing alongside ultra-fast device operation presents formidable techno-economic challenges. Here, we explored a modified version of adhesion lithography (a-Lith) to create coplanar nanogap zinc oxide (ZnO) Schottky diodes for application in diode-logic arithmetic circuits. The planar ZnO diodes offer highly scalable manufacturing and combine high current rectification (> 106) with low reverse currents (≈80 pA) and a remarkable cut-off frequency of over 25 GHz. Engineering the topologies of the planar ZnO diodes enables their facile monolithic integration into multi-bit AND and OR gates over 4-inch glass wafers. By integrating several such logic gates, we demonstrated fully functional monolithic 2-bit Half-Adder circuits, the primary component of an arithmetic logic unit. The work offers an alternative method for developing fast large-area electronics that could lead to a new family of logic circuitry.