Investigation of Ni/Au-contacts on p-GaN annealed in different atmospheres

Mistele, D.; Fedler, F.; Klausing, H.; Rotter, Thomas; Stemmer, J.; Semchinova, O.; Aderhold, J.

doi:10.1016/s0022-0248(01)01250-7

Cited by 28 publications

(21 citation statements)

References 12 publications

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“…Apart from that, in a tube furnace, although we used flowing nitrogen, there could be a certain amount of oxygen present which will lead to the oxidation of the contacts. This has been claimed to be true by Mestele et al where they have stated that annealing in nitrogen also resulted in the formation of NiO at higher temperatures [9], which is in agreement with our 700 °C sample, which has the lowest SCR in all conditions. Oxidation of the contacts can occur even with the presence of a very small amount of oxygen [9].…”

Section: Electrical Behavioursupporting

confidence: 93%

“…High quality n-GaN ohmic contacts with low specific contact resistivity (SCR) ranging from 10 -5 to 10 -8 Ωcm 2 have been vastly developed [5 -7]. However, there is much more investigation yet to be done in producing a high quality ohmic contact on p-GaN with a low contact resistance, as the lowest reported value is in the range of 10 -4 Ωcm 2 [8][9][10]. The acceptable value of contact resistance for producing an efficient and high performance device is below 10 -4 Ωcm 2 [11,12].…”

Section: Introductionmentioning

confidence: 99%

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Thermal stability of Ni/Ag contacts on p‐type GaN

Hassan

Lee

Yam

et al. 2004

phys. stat. sol. (c)

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Contact technology remains an important factor for electronic and optical devices in the field of wide band gap semiconductors. To fabricate reliable, efficient, high performance devices and circuit, it is essential to develop high quality and thermally stable contacts to GaN-based material. Making low-resistance ohmic contact is difficult for wide band gap semiconductors, especially p-GaN due to difficulty in achieving high carrier concentration, and the absence of suitable metals which have a work function larger than the bandgap and electron affinity of GaN. In this work, we report on the thermal stability and morphological investigation of Ni/Ag contacts on p-GaN. Different annealing temperatures (300 °C -800 °C) were investigated, as thermally stable metal-semiconductor contacts are essential for high quality devices. Cryogenic cooling after heat treatment was also performed to determine the effects of this treatment on the characteristics of the contacts. Specific contact resistivity (SCR) determined using transmission line method (TLM) and scanning electron microscopy (SEM) measurements were carried out to the asdeposited, annealed, and annealed-and-cryogenically treated contacts where the electrical behavior and the surface morphology of each of these conditions were compared.

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Section: Electrical Behavioursupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Thermal stability of Ni/Ag contacts on p‐type GaN

Hassan

Lee

Yam

et al. 2004

phys. stat. sol. (c)

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“…Contacts to p-type GaN have been particularly challenging, since it is difficult to grow samples with a high enough carrier concentration to promote field emission through the Schottky barrier. Due to the complexity of metallurgical contacts, various approaches have been tried, including chemical surface treatments, [3][4][5][6][7] plasma cleaning, [8][9][10] metal deposition techniques ͑sputtering, electron beam, or thermal deposition͒, [11][12][13] contact annealing in a variety of ambients, 14,15 and use of bilayers 16 -18 or multilayers [19][20][21] of various metals.…”

Section: Introductionmentioning

confidence: 99%

X-ray photoemission determination of the Schottky barrier height of metal contacts to n–GaN and p–GaN

Rickert

Ellis

Kim

et al. 2002

Journal of Applied Physics

106

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Synchrotron radiation-based x-ray photoemission spectroscopy was used to study the surface Fermi level position within the band gap for thin metal overlayers of Au, Al, Ni, Ti, Pt, and Pd on n-GaN and p-GaN. Nonequilibrium effects were taken into account by measuring the Fermi edge of the metal overlayer. There are two different behaviors observed for the six metals studied. For Au, Ti, and Pt, the surface Fermi level lies about 0.5-eV higher in the gap for n-type than for p-type GaN. For Ni, Al, and Pd, the surface Fermi level position is independent of doping, but varies from one metal to the other. Results for Ni, Pd, and Al fit a modified Schottky-Mott theory, while Au, Ti, and Pt demonstrate a more complex behavior. Atomic force microscopy was used along with photoemission to investigate the growth mode of each metal on the GaN surface.

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“…For improving the optical transparency of the contacts, metallization structures based on ZnO have been used. From among the contact structures on p-GaN, the most advantageous appeared to be be composition Au/Ni/p-GaN, [9][10][11][12][13][14][15][16][17][18], because of its relatively good values of the contact resistance and good optical transparency. On annealing the contact in oxygen ambient, reduction of the contact resistance has been reported as explained by several models, see Ho et al [9,10], Koide et al [11] and Jang et al [14].…”

Section: Introductionmentioning

confidence: 99%