Simulation of slow current transients and current collapse in GaN FETs

Abstract

Two-dimensional transient simulations of GaNMESFETs are performed in which a three-level compensation model is adopted for a semi-insulating buffer layer, where a shallow donor, a deep donor and a deep acceptor are considered. When the drain voltage V D is raised abruptly (while keeping the gate voltage V G constant), the drain current I D overshoots the steady-state value, and when V D is lowered abruptly, I D remains a low value for some periods, showing drain-lag behavior. These are explained by the deep donor's electron capturing and electron emission processes. We also calculate a case when both V D and V G are changed abruptly from an off point, and quasi-pulsed I-V curves are derived from the transient characteristics. It is shown that the drain currents in the pulsed I-V curves are rather lower than those in the steady state, indicating that so-called current collapse could occur due to deep levels in the semi-insulating buffer layer. It is also shown that the current collapse is more pronounced when V D is lowered from a higher voltage during turn-on, because the trapping effects become more significant.

In‐situ passivation combined with GaN buffer optimization for extremely low current dispersion and low gate leakage in Si3N4/AlGaN/GaN HEMT devices on Si (111)

“…These dispersion effects have been intensively studied (see e.g. [5][6][7]): traps responsible for performance degradation are essentially located either at the surface of the device, or in the GaN buffer layer.…”

(Invited) Epitaxial Growth of III-Nitrides on Silicon Substrates

“…These dispersion effects have been intensively studied (38)(39)(40): traps responsible for performance degradation are essentially located either at the surface of the device, or in the GaN buffer layer. To address the first issue, ex-situ device passivation is widely used.…”

“…We have demonstrated that it is possible to achieve extremely uniform crack-free and flat AlGaN/GaN HEMT epi wafers on 150 mm Si substrates with reasonable bow, but despite of the record performance displayed by AlGaN/GaN HEMT devices, also when deposited on Si substrates, they are known to suffer from trap effects that either reduce their RF performance (so-called "DC-RF dispersion"), or are responsible for the degradation of the transistor switching characteristics (slow current transients). These dispersion effects have been intensively studied (38)(39)(40): traps responsible for ECS Transactions, 33 (6) 833-842 (2010) performance degradation are essentially located either at the surface of the device, or in the GaN buffer layer. To address the first issue, ex-situ device passivation is widely used.…”