Influence of Process Technology on DC-Performance of GaN-Based HFETs

Mistele, D.; Rotter, Thomas; Bougrioua, Z.; Marso, Michel; Roll, H.; Klausing, H.; Fedler, F.; Semchinova, O.; Moerman, Ingrid; Graul, J.

doi:10.1002/1521-396x(200212)194:2<452::aid-pssa452>3.0.co;2-n

Cited by 2 publications

(1 citation statement)

References 13 publications

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“…First, the gate currents are lowest for the NH 4 S x treatment and not for the oxidized surfaces. Second, the highest I Dmax is found with oxidized surfaces, also in contrast to the AlGaN/GaN sample, but coinciding with results measured earlier on other GaN/AlGaN/GaN samples [29]. Third, the nitrogen plasma does not lead to a degradation of the channel current, and even more, it shows the lowest |V th | of all treatments in contrast to the AlGaN/GaN transistor sample.…”

Section: The Algan/gan Transistor With a Thin Gan-cap Layersupporting

confidence: 87%

Engineering and impact of surface states on AlGaN/GaN-based hetero field effect transistors

Mistele¹,

Katz²,

Horn

et al. 2005

Semicond. Sci. Technol.

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This work investigates the impact and origin as well as the electrical behaviour of surface states of AlGaN/GaN-based heterostructure field effect transistors (HFETs). Different GaN-cap layers were grown on top of AlGaN-barrier layers, and the active transistor surface areas were treated chemically differently. The investigations show that one relevant surface state at the AlGaN/GaN surface is that of donor-like N-vacancies. Surface plasma treatments with O 2 -and N 2 -plasmas on structures with and without GaN-cap layers reveal very different electrical dc behaviour of AlGaN/GaN-based HFETs. Band structure simulations and considerations explain the different character of surface states and the impact on the dc channel current as well as the influence on threshold voltage and barrier height by Fermi-level pinning. N-vacancies on the surface of AlGaN/GaN HFETs are ionized and therefore very sensitive to N 2 -treatment, whereas on GaN/AlGaN/GaN surfaces they remain neutral and do not affect n S and I D significantly. Oxidation, however, also introduces acceptor-like surface states, which become ionized only in the case of GaN capping, leading to an additional positive charge at the upper heterojunction and increasing negative charge in the channel. It is further shown that 30 nm low-temperature grown GaN capping drastically reduces the gate leakage, leading to a transistor with insulated gate characteristics.

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Section: The Algan/gan Transistor With a Thin Gan-cap Layersupporting

confidence: 87%

Engineering and impact of surface states on AlGaN/GaN-based hetero field effect transistors

Mistele¹,

Katz²,

Horn

et al. 2005

Semicond. Sci. Technol.

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Incorporation of dielectric layers into the processing of III-nitride-based heterostructure field-effect transistors

Mistele

Rotter

Horn

et al. 2003

Journal of Elec Materi

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Dielectric layers within III-nitride transistor technology can act either as passivation layers or as gate-dielectric layers. In this paper, we reflect on both issues and present novel approaches of dielectric schemes. In both cases, the elimination of surface traps or, more generally, of surface states is a key issue in obtaining improved device performance. As gate dielectrics, we introduced and investigated thermally and photoelectrochemically generated Al x Ga 2-x O 3 , SiO 2 , the combination of Al x Ga 2-x O 3 and SiO 2 (tandem-dielectric stack), and e-beam-deposited Al 2 O 3 . These dielectric layers serve simultaneously as a passivation layer. In addition, we introduced plasma-enhanced chemical-vapor deposition (PECVD)-deposited SiN x for passivation. The results highlight the importance of passivation and the introduction of gate dielectrics and emphasize the relationship between surface states and improved direct-current (DC) performance. Backed by additional measurements, we propose a different gateleakage mechanism for heterostructure field-effect transistor (HFET) and metal-oxide semiconductor heterostructure field-effect transistor (MOSHFET) devices.

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Influence of Process Technology on DC-Performance of GaN-Based HFETs

Cited by 2 publications

References 13 publications

Engineering and impact of surface states on AlGaN/GaN-based hetero field effect transistors

Engineering and impact of surface states on AlGaN/GaN-based hetero field effect transistors

Incorporation of dielectric layers into the processing of III-nitride-based heterostructure field-effect transistors

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