Project Details
Projekt
Planar and Vertical Junctions for innovative GaN-Based High-Power Devices
Subject Area
Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
Term
since 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 462676277
The development of group III nitrides has started a new era of high-frequency and high-power electronics. With the surge in regenerative energy sources, electric vehicles, data centres and many more mobile and energy-hungry applications, more efficient, compact and economical power conversion systems are required. In this context, a superior Baliga Figure of Merit is one factor, which promises significant potential for GaN-based power electronics (PE).Its workhorse is the lateral AlGaN/GaN HFET, which has reached commercial maturity in the 600 V regime. Generally, the vertical device geometry is preferred due to significant scaling benefits (as the maximum operating voltage can be scaled without compromising wafer area) and improved isolation properties. Electric field peaks are buried in the bulk, rendering vertical devices less prone to surface-related breakdown and parasitic effects like current collapse. Vertical power devices rely on specific types of 3D field-shaping and current-guiding (hetero)structures to ensure low leakage currents and high breakdown voltages. However, the failure of dopant implantation and diffusion processes in GaN leaves selected-area growth (SAG) as the most viable option. SAG has already yielded promising results, but a still relatively immature state is preventing the commercialization of vertical PE devices based on GaN. Material issues, especially linked to defects and non-ideal interfaces, are far from being solved. In addition to the high cost of native GaN substrates, a lack of knowledge of microstructure and defect characteristics and immature fabrication processes have prevented the development of a viable vertical GaN device technology.In this project, a systematic analysis of growth- and process-related defects and microscopic properties of p-n junctions and heterojunctions will be conducted. Compound Semiconductor Technology (CST) of RWTH Aachen University will employ SAG processes to create planar and vertical p-n junctions and heterojunctions in specific test structures for electrical and microscopic characterization. The Semiconductor Physics group at OvGU Magdeburg will perform detailed micro- and nanoscopic studies via (scanning) transmission electron microscopy ((S)TEM), cathodoluminescence (STEM-CL) spectroscopy, electron beam induced current (STEM-EBIC) measurements as well as time-of-flight transport analysis to identify defects, characterize carrier and exciton transport/dynamics and link these to electrical data and growth/processing conditions. This, complemented by physical modelling, will generate a deep understanding of the impact of defects and processes on the macroscopic material, interface and device properties and lead to novel strategies to fabricate PE devices. Finally, improved junction barrier Schottky diodes (JBS), vertical-channel junction field effect transistors (vc-JFET) or current aperture vertical electron transistors (CAVET) will be demonstrated.
DFG Programme
Priority Programmes
Subproject of
SPP 2312:
Energy Efficient Power Electronics "GaNius"
Co-Investigators
Privatdozent Dr. Frank Bertram; Dr. Holger Kalisch
