Origin of kink effect in AlGaN/GaN high electron mobility transistors: Yellow luminescence and Fe doping

AlGaN/GaN high electron mobility transistors (HEMTs) with different Fe-doping density were studied using electrical and optical analysis to gain insight into the nature of traps responsible for the kink effect in electrical characteristics. Kink effect has been previously suggested to result from direct trapping of carriers in defects related to yellow luminescence (YL) centers. However, the results demonstrate that YL is suppressed by Fe doping, whereas the kink effect is not affected to the same extent. YL related defect states are therefore not exclusively responsible for the kink effect, suggesting a more complex trapping mechanism to affect device output characteristics.