Origin of the Kink Effect in AlInN/GaN High Electron-Mobility Transistor

Abstract

Kink effect is observed in Al0.83In0.17N/GaN high electron mobility transistor by measuring ID-VDS characteristics at a low sweep rate. It is inferred that the kink is induced due to the trapping/detrapping of charge carriers at deep levels present in the GaN buffer in the gate–drain access region. The detrapping of charge carriers from the deep levels is by the hot-electron-assisted mechanism. Two types of traps with activation energies, 0.29 eV (donor-like) and 0.57 eV (acceptor-like) were extracted by temperature-dependent transient drain current analysis. It is concluded that the deep-acceptor-like trap with a large emission time constant is responsible for the kink effect.

Substrate Bias Stress Induced Kink Effect in GaN-on-Silicon High-Electron-Mobility Transistor

“…The region for V DS < V DS,kink is referred to as the "pre-kink," and for V DS > V DS,kink is referred to as the "post-kink" region. It should be noted that in our previous study [14], the kink was observed in the output characteristics of AlInN/GaN-on-SiC HEMTs, which are mainly used in RF applications. The kink in that study was observed in the static output characteristics, only when a low sweep rate (0.15 V/s) was adopted without any pre-stressing, as shown in [14, Fig.…”

“…However, the V th and g m,max values are almost saturated for stress times greater than 30 seconds. Therefore, we have The kink effect observed in GaN-based HEMTs can be explained by two different mechanisms [14]: 1) Inter-band impact ionization in the GaN channel, and 2) Trapping/detrapping of charge carriers which are trapped at the deep levels present in different epitaxial layers of the wafer. However, we did not observe any bump in gate leakage characteristics as shown in the inset of Fig.…”

“…Fig. 3 (a) shows that V DS,kink has a nonmonotonic behavior as a function of gate-to-source voltage (V GS ), where V DS,kink first decreases as V GS is increased from −5 to −3.5 V, and then increases as the gate voltage is further increased from −3.5 to 0 V. Such non-monotonic behavior of V DS,kink as a function of V GS suggests that the de-trapping mechanism is hot-electron assisted and not fieldassisted [14], [16], [17]. We studied the post-stress effect of different substrate bias polarities on the trapping mechanism and the kink amplitude in the measured output characteristics with the substrate either in floating or grounded conditions.…”

“…Switching of the substrate bias stress (V sub ) from +V sub to 0 V is analogous to the situation when V sub-S is switched from +V DD to 0 V for HS transistor in V DD substrate bias configuration, and for LS transistor in toggling substrate bias configuration as explained in the introduction. In the kink region, at higher V DS the channel electrons are accelerated by the peak electric field present at the gate edge on the drain side and acquire a sufficient amount of kinetic energy to become hot [14], [16]. Some of these hot electrons are injected toward the UID-GaN/GaN:C interface, where they knock out/de-trap the trapped electrons from the negatively charged acceptor-like traps.…”

Non-Thermal Annealing of Gamma Irradiated GaN HEMTs with Electron Wind Force

“…Interestingly, the thermally annealed sample showed kinks in drain current near V g ≈ −2 V and −3 V. Along with the significant increase in the leakage current, the data suggests the generation of additional traps in the GaN buffer or AlGaN barrier layer. 38,39 To obtain insights into the structural/crystal quality differences between the EWF and thermal annealing, we performed micro-Raman spectroscopy. Measurements were taken in a backscattering configuration with unpolarized detection, enabling the A 1 (LO) and E 2 (high) phonon modes of GaN to be measured simultaneously.…”