SCALE Heavy Ion-Induced Degradation in Gallium Nitride High Electron Mobility Transistors

Joshua Gray of Vanderbilt University presented as part of the Vanderbilt Seminar Series.

Heavy‑ion irradiation of gallium‑nitride high‑electron‑mobility transistors (GaN‑HEMTs) presents a critical reliability challenge for space‑qualified power electronics. The resource examines the formation of a catastrophic leakage path within the GaN buffer that electrically shorts the source and drain, a failure mode that threatens device operation under the high‑bias conditions typical of satellite power systems. Understanding this mechanism is essential for designing radiation‑hard GaN devices that meet stringent size, weight, and power constraints.
The investigation combines experimental ion‑beam testing with detailed failure analysis and technology‑computer‑aided design (TCAD) simulation. Devices are biased in the off‑state while exposed to ions of varying linear energy transfer (LET) and incidence angles, revealing degradation trends linked to bias voltage and LET magnitude. Leakage‑current measurements show permanent, additive increases spanning several orders of magnitude, indicating the creation of irreversible conductive channels in the buffer. Cross‑sectional analysis and TCAD modeling reproduce the observed short‑circuit behavior, linking trap‑filled buffer regions to the observed sub‑threshold leakage and confirming the hypothesized worst‑case ion trajectory through the two‑dimensional electron gas (2‑DEG). Angle‑sensitivity data, although limited, suggest that non‑vertical incidence does not exacerbate degradation relative to the nominal vertical path.