AlGaN/GaN high electron mobility transistors (HEMTs) showed its promising performance in high power and high frequency, which can be used for applications such as satellite-based communication networks, inverter units in hybrid electric vehicles and advanced radar systems. However, intrinsic defects and defects generated during the device fabrication degraded HEMT performance, such as drain current collapse, high gate leakage, and lower rf power density and power add efficiency. Furthermore, subsequent electrical stressing of the HEMTs during operation leads to creation of more traps and further device degradation through various mechanisms, including gate contact sinking, shallow trap formations, and the inverse piezoelectric effect. It is highly desirable to have non-destructive methods available to identify the activation energies of the defects and spatial location of trap states in HEMT. A sub-bandgap optical pumping technique was developed to identify trap locations in AlGaN/GaN HEMTs. By varying photon fluxes, the traps with different activation energies appeared at different photon flux levels. This implies that the defects originate at different physical locations in the HEMT. The locations of the traps identified with the sub-bandgap optical pumping methods confirmed by gate pulse measurements under optical pumping.
Fan Ren, Stephen J. Pearton, Tsung Sheng Kang, David J. Cheney, and Brent P. Gila, "Use of sub-bandgap optical pumping to identify defects in AlGaN/GaN high electron mobility transistors (Conference Presentation)," Proc. SPIE 10104, Gallium Nitride Materials and Devices XII, 101041A (Presented at SPIE OPTO: February 01, 2017; Published: 19 April 2017); https://doi.org/10.1117/12.2251166.5391659249001.
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