A Double-Pulse Technique for the Dynamic I/V Characterization of GaN FETs

Abstract

Standard dynamic characterization methods based on periodic narrow-pulse low duty-cycle excitation waveforms provide suboptimal I/V curves when used along with GaN field effect transistors (FETs), due to complex nonlinear charge trapping effects. Thus, a double-pulse technique for the dynamic characterization of GaN FETs is here presented. The double-pulsed I/V characteristics are shown to be not only isothermal but also corresponding to a fixed charge trapping state.Index Terms-Electrothermal effects, energy states, field effect transistors (FETs), gallium nitride, pulse measurements.

A new nonlinear model extraction methodology for GaN HEMTs subject to trapping effects

“…Since the minimum pulse width of present high-power IN pulser systems is higher than the time constants associated to the charge carrier trapping, it is the Vos peak voltage that imposes the trapping state, whenever we pulse from a lower Vos to a higher one (step up) [3]. On the other hand, when the Vos is pulsed from a higher value to a lower one (step down), the instantaneous ios value depends on the previous steady state Vos voltage due to the long time constant associated to the detrapping process.…”

“…Unfortunately, breakdown or quiescent dissipation power conditions may prevent pulsing from such a high VDSQ. If that is the case, we can use a double-pulse technique [3], where a fIrst pulse is used to set the desired high VDSQ, whose duration is considerably higher than the trap charging time-constants, but sufficiently smaller than the self-heating time constants, or, at least, sufficiently small to prevent burning the device.…”

“…Most of these works assume that the drain-lag effects on the IN curves can be modeled by changing the intrinsic threshold voltage, VT. Consequently, they use an additional circuit to change the VT voltage of a previously extracted non-isodynamic iDS model. However, with this extraction procedure, the iDS model coefficients are extracted to fit the measured I!V curves with many different trapping states [3], requiring a complicate function to produce the control voltage used to change the threshold voltage.…”

“…This uses a double-pulse technique [3] to set iso-dynamic IN curves, where the respective trapping state is imposed by the leading pulse VDS preset. These are then used to correctly model the threshold voltage variation between each state.…”

Pulsed I /V and S -parameters measurement system for isodynamic characterization of power GaN HEMT transistors

“…There are two main approaches to characterize these new devices: (1) Continuous wave (CW) excitations to cover the entire I / V plane, which implies a complicated curve‐fitting process to simultaneously extract the resistive and reactive components of the device. (2) Pulsed I / V and S ‐parameter measurements, for which a system that allows the generation of very fast, high‐power, and arbitrary waveform pulses is necessary. In these last ones, the capability to generate arbitrary bias signals is of remarkable importance, because it allows to generate specific waveforms that are necessary to guarantee isothermal measurements and avoid dispersive phenomena .…”