Fabrication of sub‐50‐nm‐gate i‐AlGaN/GaN HEMTs on sapphire

Endoh, Akira; Yamashita, Yoshimi; Ikeda, Keiji; Higashiwaki, Masataka; Hikosaka, Kohki; Matsui, Toshiaki; Hiyamizu, S.; Mimura, Takashi

doi:10.1002/pssc.200303335

Cited by 36 publications

(23 citation statements)

References 11 publications

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“…A level below 1 m has been achieved. 2,3 In these devices, the gate leakage current includes not only one-dimensional transport vertical to the Schottky interface but also lateral electron injection to the AlGaN surface from the gate edge. 4 Here, we have to pay attention to laterally injected charges to surface electronic states because they can cause instability in device operation.…”

Section: -3mentioning

confidence: 99%

Mechanism of surface conduction in the vicinity of Schottky gates on AlGaN∕GaN heterostructures

Kotani

Tajima

Kasai

et al. 2007

Applied Physics Letters

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Lateral surface leakage current ͑I s ͒ on an AlGaN / GaN heterostructure was systematically investigated by using a two-parallel gate structure with a gap distance ͑L GG ͒ of 200 nm-5 m. The surface current I s systematically increased as L GG decreased. A simple resistive layer conduction that should show 1 / L GG dependence failed to account for the drastic increase in I s when L GG was reduced to less than 1 m. However, no dependence on L GG was seen in vertical current that flows in the Schottky interface. The I s showed a clear temperature dependence proportional to exp͑−T −1/3 ͒, indicating two-dimensional variable-range hopping through high-density surface electronic states in AlGaN. A pronounced reduction in surface current of almost four orders of magnitude was observed in a sample with SiN x passivation.

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Section: -3mentioning

confidence: 99%

Mechanism of surface conduction in the vicinity of Schottky gates on AlGaN∕GaN heterostructures

Kotani

Tajima

Kasai

et al. 2007

Applied Physics Letters

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“…[15][16][17][18][19][20][21] The f T saturation in the AlGaN/GaN HFETs appears even at the gate length of around 200 nm that is longer than that of the InP HFETs. Although this significantly impedes the devices working at higher frequencies with the reduction of the gate length, its mechanism is not understood yet.…”

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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“…Millimetre-wave (30 to 300 GHz) operations are achieved by simply reducing the gate length L g . We fabricated sub-100-nm-gate AlGaN/GaN HEMTs and demonstrated that they exhibited true device operation down to L g =25 nm [2]. Furthermore, cryogenic operations of the HEMTs increase the cutoff frequency f T [3].…”

mentioning

confidence: 96%

Cryogenic characteristics of sub‐100‐nm‐gate AlGaN/GaN MIS‐HEMTs

Endoh

Watanabe

Yamashita

et al. 2008

Phys. Status Solidi (c)

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We measured DC and RF characteristics at 300 and 16 K of sub‐100‐nm‐gate AlGaN/GaN metal‐insulator‐semiconductor (MIS) high electron mobility transistors (HEMTs) that had SiN/SiO2/SiN triple‐layer insulators. The drain‐source current and the maximum transconductance increased as expected. We observed an increase of 14 to 28% in the value of cutoff frequency fT at 16 K over that at 300 K. At 16 K, we obtained a maximum fT of 176 GHz at a gate length Lg of 45 nm. We estimated the average electron velocity under the gate by a transit time analysis. The average velocities were 2.2 × 107 cm/s at 300 K and 2.7 × 107 cm/s at 16 K. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Fabrication of sub‐50‐nm‐gate i‐AlGaN/GaN HEMTs on sapphire

Cited by 36 publications

References 11 publications

Mechanism of surface conduction in the vicinity of Schottky gates on AlGaN∕GaN heterostructures

Mechanism of surface conduction in the vicinity of Schottky gates on AlGaN∕GaN heterostructures

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

Cryogenic characteristics of sub‐100‐nm‐gate AlGaN/GaN MIS‐HEMTs

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