Influence of different carbon doping on the performance and reliability of InAlN/GaN HEMTs

This paper studies the impact of C-doped GaN buffers on the dynamic performance and reliability of InAlN/GaN high electron mobility transistors. The analysis carried out on two different families of devices with different doping levels shows that carbon induces negligible differences in DC characteristics, which can be mainly ascribed to process variability. However, carbon doping is found to have a strong impact on the trapping characteristics: pulsed evaluation shows a significant current collapse, as well as dynamical shift in threshold voltage and transconductance drop. Drain current transient investigation reveals two main traps with apparent activation energy of 0.89 eV (T-2) and 1.05 eV (T-1), whose amplitudes are found to be correlated with carbon doping. A more detailed analysis suggests that trap T-2 is located in the buffer layer. And that traps behave as a line defect. Finally, the reliability tests demonstrate that the use of high carbon doping does not significantly influence the robustness of the devices with respect to DC OFF-state stress. (C) 2014 Elsevier Ltd. All rights reserved