An electric-opto combined measurement method for identifying filled traps in the off-state of HEMTs with high spatial resolution

Traps filled in the off-state of high electron mobility transistors (HEMTs) are a primary factor contributing to the performance instability of power devices. These traps capture leakage electrons, causing instantaneous current fluctuations and drift of the threshold voltage. Realizing high spatial resolution measurements for off-state filled traps (OFTs) has become a prerequisite for optimizing device structure and exploring the device failure mechanism. However, the existing methods mainly detect the overall integral result of traps and are unable to indicate the in-plane distribution, which is unsatisfactory for studying the details of trap effects. In this paper, an approach for detecting the concentration and spatial distribution of OFT in GaN HEMTs has been proposed. The time constant and the energy level of OFT were first measured through the current transient analysis, and the local OFT intensity was then confirmed in off-state by measuring the change in electric field based on Raman spectroscopy. By adjusting the measurement position, the distribution of the OFT throughout the device is obtained. This method would contribute to the optimized design of wide-bandgap semiconductors.