Simulating RF Performance of Proton Irradiated AlGaN/GaN High Electron Mobility Transistors (HEMT)s

Due to their relative radiation hardness, High Electron Mobility Transistors (HEMTs) with an AlGaN/GaN heterostructure are of high interest for space applications. Many studies have been performed to quantify the level of degradation due to proton radiation, with the majority being focused on the effects on the DC or steady-state performance. Fewer studies have evaluated degradation of the radio frequency (RF) performance due to proton radiation. Chen et al. caution that degradation due to proton irradiation has a more measurable impact on the RF performance in comparison to the DC performance [1]. In particular, gate lag and increases in both channel resistance and device capacitance due to fast bulk and surface traps contribute more notably to RF degradation than to DC degradation [1]. Understanding the dynamics of these traps is required for modeling and simulation of GaN HEMTs for RF applications.       

In this paper, we aim to identify the necessary input parameters for future RF simulation of radiation effects on AlGaN/GaN HEMTs. In previous work, we have found that donor traps have a larger role than previously thought on the magnitude of DC performance degradation. We use experimental techniques to identify the donor trap lifetimes and energies, both of which are incorporated into a transient simulation of the HEMT and compared to results obtained experimentally. The experiments are long-term transient measurements of drain current after a step in gate voltage for various temperatures, resulting in the establishment of capture and release time constants associated with donor traps.

(1)    J. Chen, E. X. Zhang, C. X. Zhang, M. W. McCurdy, D. M. Fleetwood, R. D. Schrimpf, S. W. Kaun, E. C. H. Kyle, and J. S. Speck, IEEE Trans. Nucl. Sci, 61 (6), 2959, (2014).