Mechanisms Underlying the Bidirectional V _T Shift After Negative-Bias Temperature Instability Stress in Carbon-Doped Fully Recessed AlGaN/GaN MIS-HEMTs

Abstract

In this brief, we investigate the bidirectional threshold voltage drift (∆VT) following negative bias temperature instability (NBTI) stress in Carbon-doped fully recessed AlGaN/GaN MIS-HEMTs. Several stress conditions were applied at different: i) gate bias (VGS,STR); ii) stress time (tSTR); and iii) temperature (T). Both negative and positive ∆VT (thermally activated with different activation energies, EA) were observed depending on the magnitude of VGS,STR. In accordance with the literature, observed ∆VT < 0 V (EA ≈ 0.5 eV) under moderate stress is attributed to the emission of electrons from oxide and interface traps. Instead, ∆VT > 0 V (EA ≈ 0.9 eV) under high stress is attributed to the increased negatively ionized acceptor trap density in the buffer associated with Carbon doping.

Hole Virtual Gate Model Explaining Surface-Related Dynamic RON in p-GaN Power HEMTs

“…The dynamic RON observed under the bias conditions under investigation in this work can be attributed to charge/discharge of hole traps present in the AlGaN barrier [11], [13]. Hole extraction (injection) during NGS(PGS) modulates the density of negatively charged traps in the gate-drain access region of the barrier, this in turn reflecting on the 2-DEG density underneath and thus RON.…”

“…Moreover, in p-GaN HEMTs, which is the common commercial technology option for normally-OFF operation (i.e., positive threshold voltage, VT) [6], the floating p-type region in the gate stack becomes a source of device instability in terms of both VT [7]- [10] and RON [11]- [13].…”

Experimental investigation on the instability for NiO/β-Ga2O3 heterojunction-gate FETs under negative bias stress

“…NiO bulk traps could explain the I GS,off variations. When NBS is applied, electrons injected from the gate are trapped by the acceptor-type bulk traps in NiO, causing the bulk traps to be negatively charged [14] . After the stress is removed, the negatively charged bulk traps block the gate leakage, resulting in a decrease in I GS,off .…”

Power Electronics Based on Wide-Bandgap Semiconductors: Opportunities and Challenges

“…An alternative option for achieving a normally-off device is the Metal-Insulator-Semiconductor-HEMT (MIS-HEMT), based on a recessed gate obtained by eliminating the AlGaN layer in the underneath region, leading to a depletion of the inversion layer (Figure 7a). An additional conformal insulating layer is needed, leading to dielectric reliability issues and instability of the threshold voltage (V th ), which are not totally solved issues [43]. A better option is the use of a p-GaN gate [44], [45], by growing an additional pdoped GaN layer before deposition of the gate contact (illustrated in Figure 7b).…”