Improved Turn-On Voltage Controllability in AlGaN/GaN Gated-Anode Diodes Using Etch Endpoint Detection Layer

AlGaN/GaN gated-anode diodes (GADs) have been proposed as microwave rectifying devices for microwave wireless power transmission (WPT) systems. However, achieving the desired turn-on voltage (
${V}_{\text {on}}$
) has posed a critical challenge due to the requirement for precise etching control. This article introduces a novel GAD structure aimed at enhancing productivity. In this new configuration, a GaN etch endpoint detection layer (GaN marker layer) is incorporated into the AlGaN layer, positioned approximately 4.5 nm away from the channel interface. During gate recess etching, the residual thickness of AlGaN is monitored using an optical interferometer. Etching is halted successfully upon detection of the GaN marker layer, signaled by an abrupt change in interference. Fabricated GADs consistently achieved the target
${V}_{\text {on}}$
of +0.20 V, exhibiting improved uniformity compared to prior GADs lacking a GaN marker layer. These devices typically demonstrated a maximum forward current of 0.69 A/mm and a reverse breakdown voltage exceeding 100 V. Additionally, a bridge-type rectifier circuit employing four GADs was simulated using a SPICE model constructed from measured pulse I–V characteristics and S-parameters. A conversion efficiency of 84% was predicted with an input power of 25.6 W (8 W/mm) at 5.8 GHz.