Lateral and Vertical β-Ga₂O₃ Transistors for Next-Generation Power Applications

The semiconductor β-Ga₂O₃, distinguished by its ultra-wide bandgap of approximately 4.8 eV, has gained substantial attention in recent years within the context of advancing the next generation of power electronic devices. The assessed high breakdown strength of 8 MV/cm and the resultant elevated Baliga’s figure of merit exceeding 3,000 signify the potential for developing significantly more compact and, consequently, efficient power converters employing this material when compared to well-established SiC and GaN technologies. Notably, lateral β-Ga₂O₃ metal-oxide-semiconductor field-effect transistor (MOSFET) devices have exhibited remarkable performances. These transistors currently manifest an average breakdown strength of up to 5.5 MV/cm and showcase record-breaking breakdown voltages reaching 10 kV. Furthermore, the power figure of merit demonstrates a continual ascent, nearly surpassing a value of 1 GW/cm², attributed to ongoing enhancements in material quality and device optimizations.<br/>This presentation aims to provide an overview on the current status of the process development for lateral and vertical β-Ga₂O₃ power transistor devices for high-voltage switching applications, with a specific focus on outcomes achieved at FBH and IKZ. For both scenarios, diverse approaches to bulk crystal growth, epitaxial layer structures, and device designs, tailored to attain the targeted performance parameters, will be deliberated, particularly in terms of breakdown voltage and channel current density. In this regard, we demonstrate the fabrication of lateral (100) β-Ga₂O₃ MOSFET devices with breakdown voltages up to 1.8 kV featuring a power figure of merit up to 155 MW/cm². Large periphery devices with a total gate width of 10 mm verify fast switching at 400 V with a turn-on switching speed up to 78 V/ns. In addition, the incorporation of p-type SnO highlights the considerable potential for realizing high-performance heterojunction SnO/Ga₂O₃ field-effect transistors.<br/>Furthermore, we present vertical (100) β-Ga₂O₃ FinFET devices exhibiting enhancement-mode characteristics and a breakdown strength of 2.7 MV/cm. A comprehensive device simulation encompassing the entire FinFET structure using Silvaco Atlas identifies electric field peaks outside the active area within the SiN_x passivation layers and Al₂O₃ gate oxide, potentially serving as primary contributors to breakdown phenomena. As a culmination of these advancements, specific challenges, both in material and device domains, are identified, necessitating prospective resolutions to overcome prevailing breakdown limitations.