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

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 (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>S</i></sub>) and junction capacitance (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$C_{\!j}$</tex-math></inline-formula>) in rectification losses. A precise balance between <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$C_{\!j}$</tex-math></inline-formula> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>S</i></sub> is crucial for optimizing the physical design of SBDs and enhancing rectifier efficiency. Thus, we present an improved loss model designed for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>S</i></sub> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$C_{\!j}$</tex-math></inline-formula>. Our results reveal that the impact of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>S</i></sub> is more significant compared to that of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$C_{\!j}$</tex-math></inline-formula> in 1–8 GHz. Then, we designed an AlGaN/GaN Schottky structure with 10 nm barrier layer thickness which reduces resistive losses of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>S</i></sub> 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 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>S</i></sub> of 3 Ω, and a commercial SBD (SBD-2, layer = 20 nm) with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>S</i></sub> of 7 Ω, both having almost the identical <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$C_{\!j}$</tex-math></inline-formula>. At 5.8 GHz, efficiency of SBD-1 achieved 80.2% with 25.4 dBm input power and 170 Ω load, while the SBD-2 reached 74.4% efficiency at 23 dBm and 300 Ω 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 Ω, highlighting the superiority of the loss model and thin barrier structure for microwave rectification.