Main goal of power semiconductors is to increase the power density, in other words to generate less and less electrical losses in the smallest possible area. Conventional silicon components are encountering their limits here. Scientists all over the world are therefore investigating new materials and components that can meet these requirements. The Ferdinand Braun Institute (FBH) has now achieved a breakthrough with transistors based on gallium oxide (ß-Ga2O3).
The newly-developed lateral MOSFETs provide a breakdown voltage of 1.8 kV and a record power figure of merit of 155 MW per square centimeter, close to the theoretical material limit of gallium oxide. At the same time, the breakdown field strengths reach 1.8 MV/cm to 2.2 MV/cm for gate-drain spacings between 2 µm and 10 µm. This is significantly higher than those of established wide bandgap semiconductors such as silicon carbide or gallium nitride.
Optimized Layer Structure and Gate Topology
In order to achieve these improvements, the FBH team tackled the layer structure and gate topology. The basis was provided by substrates from the Leibniz Institute for Crystal Growth with an optimized epitaxial layer structure. As a result, the defect density could be reduced and electrical properties improved. This leads to lower on-state resistances.
The gate topology has been further optimized, allowing to reduce high field strengths at the gate edge. This in turn leads to higher breakdown voltages.
K. Tetzner, et al., Lateral 1.8 kV β -Ga2O3 MOSFET With 155 MW/cm² Power Figure of Merit, IEEE Electron Device Letters, vol. 40, no. 9, pp. 1503-1506, Sept. 2019. DOI: 10.1109/LED.2019.2930189