Slow transients observed in AlGaN HFETs: Effects of SiN/sub x/ passivation and UV illumination

Koley, Goutam; Tilak, V.; Eastman, L.F.; Spencer, Michael G.

doi:10.1109/ted.2003.812489

Cited by 208 publications

(122 citation statements)

References 15 publications

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“…Using scanning Kelvin probe microscopy, Sabuktagin et al 24 and Koley et al 57 have directly observed charge injection at the gate edge. Using the 2DEG-sensing bars, such an effect can also be observed.…”

Section: F Charge Injection Effect At the Gate Edgementioning

confidence: 99%

Non-localized trapping effects in AlGaN/GaN heterojunction field-effect transistors subjected to on-state bias stress

Hu¹,

Hashizume²

2012

Journal of Applied Physics

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Evidence of space charge limited flow in the gate current of AlGaN/GaN high electron mobility transistors Appl. Phys. Lett. 100, 223504 (2012) Off-state breakdown and dispersion optimization in AlGaN/GaN heterojunction field-effect transistors utilizing carbon doped buffer Appl. Phys. Lett. 100, 223502 (2012) Charge transport and trap characterization in individual GaSb nanowires J. Appl. Phys. 111, 104515 (2012) The asymmetrical degradation behavior on drain bias stress under illumination for InGaZnO thin film transistors Appl. Phys. Lett. 100, 222901 (2012) Mechanism of random telegraph noise in junction leakage current of metal-oxide-semiconductor field-effect transistor J. Appl. Phys. 111, 104513 (2012) Additional information on J. Appl. Phys. For AlGaN/GaN heterojunction field-effect transistors, on-state-bias-stress (on-stress)-induced trapping effects were observed across the entire drain access region, not only at the gate edge. However, during the application of on-stress, the highest electric field was only localized at the drain side of the gate edge. Using the location of the highest electric field as a reference, the trapping effects at the gate edge and at the more distant access region were referred to as localized and non-localized trapping effect, respectively. Using two-dimensional-electron-gas sensing-bar (2DEG-sensing-bar) and dual-gate structures, the non-localized trapping effects were investigated and the trap density was measured to be $1.3 Â 10 12 cm À2 . The effect of passivation was also discussed. It was found that both surface leakage currents and hot electrons are responsible for the non-localized trapping effects with hot electrons having the dominant effect. Since hot electrons are generated from the 2DEG channel, it is highly likely that the involved traps are mainly in the GaN buffer layer. Using monochromatic irradiation (1.24-2.81 eV), the trap levels responsible for the non-localized trapping effects were found to be located at 0.6-1.6 eV from the valence band of GaN. Both trap-assisted impact ionization and direct channel electron injection are proposed as the possible mechanisms of the hot-electron-related non-localized trapping effect. Finally, using the 2DEG-sensing-bar structure, we directly confirmed that blocking gate injected electrons is an important mechanism of Al 2 O 3 passivation. V C 2012 American Institute of Physics.

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Section: F Charge Injection Effect At the Gate Edgementioning

confidence: 99%

Non-localized trapping effects in AlGaN/GaN heterojunction field-effect transistors subjected to on-state bias stress

Hu¹,

Hashizume²

2012

Journal of Applied Physics

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“…9 The current collapse effects have often been observed AlGaN/GaN HFETs under quiescent gate stress 10 or pulsemode gate stress. 11,12 The collapse is also induced by drain stress. 13,14 Hasegawa and coworkers 5 explained that the charging effects of the surface electronic states, consisting of a U-shaped surface state continuum and V N -related nearsurface deep donor, play a dominant role for the current collapse, 5 as schematically shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

Lateral tunneling injection and peripheral dynamic charging in nanometer-scale Schottky gates on AlGaN/GaN hetrosturucture transistors

Kotani¹,

Kasai²,

Hashizume³

et al. 2005

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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The gate leakage and gate control characteristics of AlGaN/GaN heterostructure field effect transistors ͑HFETs͒ were systematically investigated in an attempt to clarify possible effects of surface states. The experiments were compared to rigorous computer simulations. We observed large amounts of leakage currents in the Schottky diodes fabricated on the AlGaN epitaxial layers. By the calculation based on a thin surface barrier model in which the effects of surface defect donor were taken into account, this large leakage was well explained by enhancement of tunneling transport processes due to the barrier thinning associated with ionization of surface-defect donor. On the other hand, the analysis on the current-voltage characteristics for the nanometer-scale Schottky contacts on AlGaN/GaN HFETs, indicated additional lateral leakage components. The comparison of the gate control characteristics between experiment and calculation clearly showed that the effective lateral expansion of gate length significantly impeded the g m enhancement by the reduction of geometrical gate length. This can be explained by the lateral electron tunneling process at the AlGaN surface stimulated by the pronounced gate leakage currents. Due to frequent tunneling transfer at the gate periphery, surface state occupancy near the gate becomes governed by the metal Fermi level, causing the dynamic surface state charging effects. This resulted in effective widening of the gate length, leading to degradation of gate control performance in AlGaN/GaN HFETs.

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“…However, all the fabricated devices had gate length/barrier thickness aspect ratios larger than 5 at least, then no short channel effect was expected to take place. Another responsible mechanism is formation of virtual gates [1][2][3][4] , where the effective gate length is virtually longer than that of geometrical size due to unintentional charging up of the surface at the gate periphery.…”

Section: Characteristics Of Fabricated Hfetsmentioning

confidence: 99%

“…It is also problem that their cut-off frequency is saturated around 100 GHz, even when the gate length is reduced less than 100 nm. Recent researches have revealed that these problems strongly relate to surfaces of GaN-based materials [1][2][3] , however, their mechanisms have not been understood enough yet.…”

Section: Introductionmentioning

confidence: 99%

Gate control, surface leakage currents, and peripheral charging in AlGaN/GaN heterostructure field effect transistors having nanometer-scale schottky gates

Kasai

Kotani

Hashizume

et al. 2006

J. Electron. Mater.

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Gate control properties together with gate leakage currents in AlGaN/GaN HFETs with nm-scale Schottky gates were investigated focusing on effects of AlGaN surfaces at the gate periphery. Fabricated AlGaN/GaN HFETs showed unexpectedly small gate length (L G )-dependence of transconductance, g m . Comparison of transfer characteristics from theory and experiment, effective L G in the fabricated devices were found much longer than geometrical size in the order of 100 nm, indicating the formation of virtual gates. Detailed analysis of the gate leakage current behaviors based on a thin surface barrier model showed the presence of strong electric field at the gate periphery. Mechanism of the virtual gate formation was discussed based on the obtained nm-scale Schottky gate behaviors.

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Slow transients observed in AlGaN HFETs: Effects of SiN/sub x/ passivation and UV illumination

Cited by 208 publications

References 15 publications

Non-localized trapping effects in AlGaN/GaN heterojunction field-effect transistors subjected to on-state bias stress

Non-localized trapping effects in AlGaN/GaN heterojunction field-effect transistors subjected to on-state bias stress

Lateral tunneling injection and peripheral dynamic charging in nanometer-scale Schottky gates on AlGaN/GaN hetrosturucture transistors

Gate control, surface leakage currents, and peripheral charging in AlGaN/GaN heterostructure field effect transistors having nanometer-scale schottky gates

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