Mechanism of radio-frequency current collapse in GaN–AlGaN field-effect transistors

Abstract

The mechanism of radio-frequency current collapse in GaN–AlGaN heterojunction field-effect transistors (HFETs) was investigated using a comparative study of HFET and metal–oxide–semiconductor HFET current–voltage (I–V) and transfer characteristics under dc and short-pulsed voltage biasing. Significant current collapse occurs when the gate voltage is pulsed, whereas under drain pulsing the I–V curves are close to those in steady-state conditions. Contrary to previous reports, we conclude that the transverse electric field across the wide-band-gap barrier layer separating the gate and the channel rather than the gate or surface leakage currents or high-field effects in the gate–drain spacing is responsible for the current collapse. We find that the microwave power degradation in GaN–AlGaN HFETs can be explained by the difference between dc and pulsed I–V characteristics.

Photoionization spectroscopy in AlGaN/GaN high electron mobility transistors

“…5,6 Although the dc effect will have an influence on the output power at high frequencies, other defect-related phenomena, such as gate lag ͑usually associated with surface states͒, specifically affects the high frequency device performance.…”

Induced strain mechanism of current collapse in AlGaN/GaN heterostructure field-effect transistors

“…We also showed that I 00 differs from I 0 much more than might be expected from transistor transfer curve nonlinearity and that this difference is a direct manifestation of the current collapse. 1 In spite of a large number of studies of the current collapse, 1-7 the physical mechanism of the effect has remained somewhat mysterious even though the phenomenon has been observed in almost all AlGaN/GaN HFETs and MOSHFETs. In this letter, we present the results of the experiments that allow us to locate the device active layer regions responsible for the current collapse.…”

“…The so-called current collapse [1][2][3][4] and long-term stability are the most important problems preventing large-scale practical usage of nitride-based heterostructure field-effect transistors ͑HFETs͒ and metal-oxide-semiconductor HFETs ͑MOSHFETs͒ in ultra-high-power microwave systems. The current collapse manifests itself as a reduction of the device current when a large alternating signal is applied to the gate.…”

Si 3 N 4 / AlGaN/GaN –metal–insulator–semiconductor heterostructure field–effect transistors

“…10 However MOSH-FET and HFET devices fabricated from the same wafer exhibit nearly the same degree of current collapse. 11 In other words, SiO 2 layer incorporation under the gate does not affect the mechanism responsible for current collapse in AlGaN/GaN HFETs. On the other hand, several groups have recently shown that Si 3 N 4 passivation in the source-gate and gate-drain regions reduces the degree of current collapse.…”