Trapping mechanisms in GaN‐based MIS‐HEMTs grown on silicon substrate

Abstract

In this work we report on the three dominant trapping mechanisms affecting the dynamic performance of a double-heterostructure GaN-based MIS-HEMT grown on silicon substrate. In the OFF-state, with high drain voltage and pinched-off 2DEG, the dominant mechanism is the charge-trapping in the gate-drain access region caused by the transversal drain-to-substrate potential. This effect causes the dynamic increase of the ON-resistance, and is positively temperature-dependent, thus of great concern for high-temperature operation. In the SEMI-ON-state, due to the presence of high V<inf>DS</inf> and relatively high I<inf>DS</inf>, an additional trapping mechanism emerges, involving the injection of hot electrons from the 2DEG into trap states located in the GaN-buffer or in the AlGaN barrier. This mechanism, critical in hard-switching operations, affects both the ON-resistance and the V<inf>TH</inf>. Finally, when the gate is positively biased (gate overdrive state) trapping of electrons happens in the gate dielectric layer(s), leading to strong metastable V<inf>TH</inf> instabilities. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

On the origin of interface states at oxide/III-nitride heterojunction interfaces

“…[13][14][15] However, the electronic states existing at such interfaces may significantly influence the device performance due to uncontrolled interface charging. [16][17][18][19][20][21][22][23] Despite the high importance of interface states at dielectric/III-N heterojunction interfaces, their origin and properties, in particular, the density distribution vs. energy, D it (E), in the wide band gap, E G , and charge type (donor-like or acceptor-like) are still not clarified. The main reason of such a situation are the extreme obstacles in the quantitative characterization of interface states by means of the electrical methods in the case of III-N heterojunction based devices because of the presence of two interfaces and very long time constants for charge emission from the deep states at room temperature (RT).…”

Characterization of capture cross sections of interface states in dielectric/III-nitride heterojunction structures

“…Consequently, in the studies and modeling of the operation of IG-type GaN-based HEMTs, the capture cross section values typical for the SiO 2 /Si interface or bulk defect levels are often inadequately assumed. [18][19][20][21][22][23] The aim of the present work is the determination and analysis of the electron capture cross sections (r) of interface states at dielectric/III-N heterojunction interfaces using a newly developed photo-electric method. This method is based on the measurement of the threshold voltage shift (᭝V th ) in a capacitance-voltage (C-V) characteristics before and after illumination using photon energies (E ph ) less than the band gap (E g ) at high temperature (T).…”

Technology and Reliability of Normally-Off GaN HEMTs with p-Type Gate

“…As in the case of normally-off transistors, the exposure to high drain bias in the off-state can trigger further trapping processes, due to the filling of surface states [8], to defects located in the (Cdoped) buffer [6], or to the injection of electrons from the substrate [38]. These trapping processes are not specific for p-GaN gate devices, and their discussion is beyond the scope of this paper.…”

“…Time-to-failure (TTF) is defined as the time necessary for reaching a gate leakage of 10 mA (measured at 8.5 V). Electroluminescence measurements (Figure 10) indicate that each of the steps in gate current corresponds to the appearance of a "hot-spot", corresponding to the creation of As in the case of normally-off transistors, the exposure to high drain bias in the off-state can trigger further trapping processes, due to the filling of surface states [8], to defects located in the (C-doped) buffer [6], or to the injection of electrons from the substrate [38]. These trapping processes are not specific for p-GaN gate devices, and their discussion is beyond the scope of this paper.…”