Current Collapse in Buffer-Free GaN-on-SiC Power Transistors: Maxwell-Wagner Effect and Related Model

Recently, the use of insulating substrates has emerged as a viable option for the fabrication of GaN power transistors exceeding 1 kV. Such structures are of interest because no doped buffer is used, so—ideally—a low dynamic <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"><roman>DSON</roman></sub> is expected. This article investigates the recoverable (and temperature dependent) current lowering induced by negative backgating in buffer-free GaN-on-SiC devices. Remarkably, we demonstrate that such an effect is not directly related to charge trapping, but to the Maxwell–Wagner effect, i.e., the charge migration at the interface between the insulating SiC substrate and the semi-insulating GaN layer. Accordingly, a model is defined and validated to simulate with great accuracy, the current decreases (and related kinetics) as a function of temperature, voltage, and time.