“Hole Redistribution” Model Explaining the Thermally Activated R _ON Stress/Recovery Transients in Carbon-Doped AlGaN/GaN Power MIS-HEMTs

Abstract

RON degradation due to stress in GaN-based power devices is a critical issue that limits, among other effects, long-term stable operation. Here, by means of twodimensional device simulations, we show that the RON increase and decrease during stress and recovery experiments in Carbon-doped AlGaN/GaN power MIS-HEMTs can be explained with a model based on the emission, redistribution, and re-trapping of holes within the Carbon-doped buffer ('hole redistribution', in short). By comparing simulation results with front-and back-gate offstate stress experiments we provide an explanation for the puzzling observation of both stress and recovery transients being thermally activated with the same activation energy of about 0.9 eV. This finds a straightforward justification in a model in which both RON degradation and recovery processes are limited by hole emission by dominant Carbon-related acceptors that are energetically located at about 0.9 eV from the GaN valence band.

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

“…EA ≈ 0.9 eV actually indicates that the observed behavior is likely caused by the dynamics of buffer acceptor traps (related to C-doping) that are energetically located at about 0.9 eV from GaN valence band edge [14]. In fact, buffer traps are known to strongly affect the behavior of AlGaN/GaN power MIS-HEMTs, as also supported by numerical simulations [15]- [20]. In this context, the thermally activated positive ∆VT (with EA ≈ 0.9 eV) under high |VGS,STR| can be attributed to hole emission from the 0.9-eV CN acceptor traps and the consequent increase in negatively ionized CN levels.…”

On the Modeling of the Donor/Acceptor Compensation Ratio in Carbon-Doped GaN to Univocally Reproduce Breakdown Voltage and Current Collapse in Lateral GaN Power HEMTs

“…Gate current was modelled by the thermionic and field emission mechanisms. The field emission component was calculated self-consistently by the simulator through a nonlocal tunnelling model based on the WKB approximation [ 16 ].…”

“…These aspects call for the correct modeling of C-related trap states in GaN transistors when performing device simulations to investigate important performance-limiting effects, such as buffer leakage and related V BD [ 13 , 14 ], dynamic R ON [ 4 , 10 , 16 ], current collapse [ 2 , 12 , 17 ], and threshold voltage instabilities [ 18 , 19 , 20 , 21 ]. In fact, both the concentration of acceptor states ( N C,A ) and donor states ( N C,D ), as well as their compensation ratio , defined as CR = N C,D / N C,A , need to be properly determined in order to reproduce the features of realistic devices and calibrate device simulation for a given technology.…”

Self-Heating and Reliability-Aware “Intrinsic” Safe Operating Area of Wide Bandgap Semiconductors—An Analytical Approach

“…VDMOS, LDMOS, HEMT) degrade differently as a function of voltage and temperature. Therefore, in practice, technology development generally reverts to detailed and time-consuming material-device-circuit-system simulations or empirically measured parameters based on early-stage products to assess performance [10], [13]- [15]. While resorting to this kind of…”