Influence of pre-etching on specific contact parameters for metal-GaN contacts

Mistele, D.; Aderhold, J.; Klausing, H.; Rotter, Thomas; Semchinova, O.; Stemmer, J.; Uffmann, D.; Graul, J.; Eberhard, Franz; Mayer, Markus; Schauler, M; Kamp, M.; Ahrens, Christian H.

doi:10.1088/0268-1242/14/7/309

Cited by 6 publications

(5 citation statements)

References 18 publications

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“…The results clearly demonstrate that the N 2 surface treatment must have a strong impact on the two-dimensional electron gas (2DEG) in the channel. Since the treatment (10 s, 100 W, 200 mTorr) is rather weak, no etching or structural defects can be made responsible for the current [23]. This understanding also confirms the fact that the Schottky behaviour is improved (figure 2(b)) by the N 2 -treatment compared to the untreated sample and the NH 4 S x -treated sample.…”

Section: The Algan/gan Transistorsupporting

confidence: 71%

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 Transistorsupporting

confidence: 71%

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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“…Fabrication of microelectronic devices often involves plasma etching or implantation on their surfaces. However, the ion bombardment process may change the stoichiometry and chemical bond of the surface region to a depth of several atomic layers and thereby affect the structural and the electronic properties of the interface or surface. − For instance, surface stoichiometry can affect the resistance of a metal contact (i.e., Ohmic contact or Schottky barrier) which is subsequently deposited on the pre-etched GaN surface. , Hence, the study of ion-induced damage to nitrides is a necessary step in optimizing processes for device fabrication. To that aim, an essential stage is the characterization of stoichiometry and structure of sputtered surfaces.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5] For instance, surface stoichiometry can affect the resistance of a metal contact (i.e., Ohmic contact or Schottky barrier) which is subsequently deposited on the pre-etched GaN surface. 6,7 Hence, the study of ion-induced damage to nitrides is a necessary step in optimizing processes for device fabrication. To that aim, an essential stage is the characterization of stoichiometry and structure of sputtered surfaces.…”

Section: Introductionmentioning

confidence: 99%

Sputtering and Etching of GaN Surfaces

Lai¹,

Yeh²,

and³

et al. 2001

J. Phys. Chem. B

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Sputtering of the GaN(0001) surface by Ar + and N 2 + ion beams is investigated using synchrotron-radiation photoemission spectroscopy. For Ar + sputtering, the N atom is preferentially removed and a Ga-enriched GaN surface is produced. The excess Ga atoms on the Ar + -sputtered surface aggregate to form metallic Ga clusters at temperatures above 623 K. A better-ordered GaN(0001)-1 × 1 surface can be obtained by N 2 + sputtering, instead of Ar + sputtering. In addition to acting as a sputtering particle, the N 2 + ion also serves as a reactant which compensates for the preferential loss of the N atom caused by physical ion bombardment. During chlorination of GaN, chlorine preferentially reacts with surface Ga atoms to form Ga chlorides. Although Ga monochloride (GaCl) is the major product formed on the N 2 + -sputtered surface, however, volatile chlorides (GaCl 2 and GaCl 3 ) are mainly produced on the Ar + -sputtered surface. The formation of volatile products on the Ar + -sputtered GaN surface may result in higher etching rates and lower etching temperatures for ionassisted chemical etching.

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“…[6][7][8][9][10][11] A comprehensive set of metals, such as Cr/Au, Pt/Au, Ti/Pt/Au, Ni/Au-Zn, Ni/Au, Ni/Si, Ni/Cr/Au, and Pd/Au, investigated for a ohmic contact on p-GaN are reported by Wenzel et al 12,13 In addition to the metal systems themselves, also investigated are the effect of surface treatments 14,15 and annealing treatments 11,[16][17][18] on q c in p-GaN.…”

Section: Ohmic Contact In P-ganmentioning

confidence: 99%

Measurement of Small Specific Contact Resistance of Metals with Resistive Semiconductors

Krishna

2007

Journal of Elec Materi

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The method to measure specific contact resistance of metals with resistive semiconductors has difficulties associated with it. These difficulties are discussed in relation to contacts on gallium nitride (GaN). The specific contact resistance of a Ni/Au contact on p-GaN after oxygen anneal was determined to be on the order of 10 )1 Wcm 2 , which is significantly higher than the best value (10 )6 Wcm 2 ) reported in the literature. However, the basic measurement of current-voltage (I-V) characteristics of the contact in determining the specific contact resistance is not significantly different. The analysis shows that in materials such as p-GaN, which is highly resistive, a low specific contact resistance may be difficult to measure by standard transmission line methods below approximately 10 )2 -10 )3 Wcm 2 in p-GaN.

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Influence of pre-etching on specific contact parameters for metal-GaN contacts

Cited by 6 publications

References 18 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

Sputtering and Etching of GaN Surfaces

Measurement of Small Specific Contact Resistance of Metals with Resistive Semiconductors

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