Development of AlGaN/GaN Schottky Diodes and Rectifiers Based on Innovative Loss Model for Wireless Power Transfer

Abstract

Reducing the Schottky barrier diode (SBD) loss is imperative for enhancing RF-dc conversion efficiency of rectifier in microwave wireless power transfer (MWPT) systems. However, existing diode models do not adequately describe the role of key loss factor-series resistance ( $R_{S}$ ) and junction capacitance ( $C_{\!j}$ ) in rectification losses. A precise balance between $C_{\!j}$ and $R_{S}$ is crucial for optimizing the physical design of SBDs and enhancing rectifier efficiency. Thus, we present an improved loss model designed for $R_{S}$ and $C_{\!j}$ . Our results reveal that the impact of the $R_{S}$ is more significant compared to that of the $C_{\!j}$ in 1–8 GHz. Then, we designed an AlGaN/GaN Schottky structure with 10 nm barrier layer thickness which reduces resistive losses of $R_{S}$ during carrier transport across the barrier layer, improving rectification efficiency. We have compared two SBD types: our thin-barrier AlGaN/GaN SBD (SBD-1, layer =10 nm) with $R_{S}$ of $3~\Omega $ , and a commercial SBD (SBD-2, layer =20 nm) with $R_{S}$ of $7~\Omega $ , both having almost the identical $C_{\!j}$ . At 5.8 GHz, efficiency of SBD-1 achieved 80.2% with 25.4 dBm input power and $170~\Omega $ load, while the SBD-2 reached 74.4% efficiency at 23 dBm and $300~\Omega $ load. This represents a 5.8% improvement in peak efficiency for SBD-1 compared to SBD-2. Furthermore, SBD-1 maintained high efficiency above 70% with input power from 17 to 28.5 dBm and load from 50 to $900~\Omega $ , highlighting the superiority of the loss model and thin barrier structure for microwave rectification.