Anomalous Source-Side Degradation of InAlN/GaN HEMTs Under High-Power Electrical Stress

Abstract

The electrical degradation of InAlN/GaN highelectron-mobility transistors (HEMTs) for millimeter-wave applications has been examined under simultaneous high VDS,stress and high IDstress electrical stress. Besides a drain current decrease and a positive threshold voltage shift, the creation of an anomalous source-side gate leakage path has been identified. We attribute this to high electric-field induced trap generation in the AlN layer directly under the gate edge on the source side. The resulting increase in gate leakage further exacerbates the degradation of the gate diode. In addition, we postulate that high power stress leads to significant device self-heating that causes gate sinking and leads to a permanent positive threshold voltage shift and drain current degradation.

Gate current degradation in W-band InAlN/AlN/GaN HEMTs under gate stress

“…Previously we have shown that under high-VDS-high-ID stress, significant degradation of the gate current takes place during the first few tens of seconds [2]. Additionally, we found that, unlike in conventional AlGaN/GaN devices where the barrier is relatively thick, the stress-induced leakage path appears on the source side [9]. This is unexpected particularly in light of conventional AlGaN/GaN HEMTs with a thicker barrier layer for which drain-side degradation dominates under similar stress conditions [10]- [12].…”

“…This is unexpected particularly in light of conventional AlGaN/GaN HEMTs with a thicker barrier layer for which drain-side degradation dominates under similar stress conditions [10]- [12]. After analyzing the difference in terms of stress conditions on the source and drain sides, we postulated a defect formation degradation mechanism caused by high electric field across the 1 nm AlN layer on the source side together with high IGstress (through the source side) coupled with significant self-heating [9].…”

“…At the end of the experiment, in order to separate permanent and recoverable degradation, we conducted a thermal detrapping step designed to detrap all electrons and reveal permanent degradation [9]. The red dots in Fig.…”