Ohmic contacts to Al-rich n -AlGaN

Mohney

et al. 2004

Journal of Elec Materi

Self Cite

Four vanadium-based contacts to n-type Al 0.6 Ga 0.4 N were compared in this work. Both V/Al/Pd/Au and V/Al/V/Au contacts with optimized layer thicknesses provided lower specific-contact resistances than did the previously reported V/Al/Pt/Au ohmic contact. Specific contact resistances of the V/Al/Pd/Au (15 nm/85 nm/20 nm/95 nm) and V/Al/V/Au (15 nm/85 nm/20 nm/95 nm) contacts were 3 ϫ 10 Ϫ6 Ω·cm 2 and 4 ϫ 10 Ϫ6 Ω·cm 2 , respectively. On the other hand, an analogous V/Al/Mo/Au contact never became ohmic, even after it was annealed at 900°C for 30 sec. Compared to the V/Al/Pd/Au contact, the V/Al/V/Au contact required a less severe annealing condition (30 sec at 700°C instead of 850°C). The V/Al/V/Au contact also provided a smoother surface, with a root-mean-square (RMS) roughness of 39 nm.

Section: Introductionsupporting

confidence: 77%

Vanadium-based ohmic contacts to n-type Al0.6Ga0.4N

Mohney

et al. 2004

Journal of Elec Materi

Self Cite

“…This result is consistent with our earlier studies of contacts to different compositions of Al x Ga 1-x N, which demonstrated that V-based contacts were optimized at lower annealing temperatures than Ti-based contacts. 1 On the other hand, we see a different trend when Ti-and V-based contacts to plasma-etched n-A 0.58 Ga 0.42 N are prepared. For V-based contacts to plasma-etched n-Al 0.58 Ga 0.42 N, the best contact was the V(20)/Al(100)/V(20)/Au(60 nm) metallization, which provided a specific contact resistance of 4.7 · 10 -4 X cm 2 when directly annealed at 800°C for 120 s in N 2 .…”

Section: Resultsmentioning

confidence: 80%

“…Recently, it has been reported that V-based contacts with similar multilayer structures can be processed at lower temperatures and provide lower specific contact resistances than Ti-based metallizations as the AlN mole fraction increases in n-Al x Ga 1-x N. 1 Minimization of contact resistance for different compositions and pretreatments of Al x Ga 1-x N can be achieved by optimization of layer thicknesses for either Ti-or V-based contacts. [1][2][3][4][5][6][7] For bottom-emitting ultraviolet light-emitting diodes, plasma etching is required to contact a buried n-type layer, but plasma etching may be damaging to the electrical and physical properties of the semiconductor surface. 8 The multilayer contacts must then be altered to accommodate the changes in the properties of the etched semiconductor and minimize contact resistance.…”

Section: Introductionmentioning

confidence: 99%

Ti/Al/Ti/Au and V/Al/V/Au Contacts to Plasma-Etched n-Al0.58Ga0.42N

Miller

Koo

Bogart

et al. 2007

Journal of Elec Materi

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Cross-sectional transmission electron microscopy was used to study annealed Ti/Al/Ti/Au and V/Al/V/Au ohmic contacts to as-received and plasma-etched n-Al 0.58 Ga 0.42 N. The reaction depth of low-resistance V-based contacts to as-received n-Al 0.58 Ga 0.42 N is very limited, unlike previously reported Ti-based contacts to n-Al x Ga 1-x N. In the present study, the Ti/Al/Ti/Au contacts to as-received n-Al 0.58 Ga 0.42 N required much higher annealing temperatures than the V-based contacts and also exhibited deeper reactions on the order of 40 nm. To achieve a low contact resistance on plasma-etched n-Al 0.58 Ga 0.42 N, different metal layer thicknesses and processing conditions were required. The Ti-and V-based contacts to plasma-etched n-Al 0.58 Ga 0.42 N exhibited both similar contact resistances and limited reaction depths, along with the presence of an aluminum nitride layer at the metallization/semiconductor interface. Metal channels penetrate the aluminum nitride layer connecting the top of the metallization to the n-Al 0.58 Ga 0.42 N. The similarity in phase formation in the contacts to plasma-etched n-Al 0.58 Ga 0.42 N is likely the reason behind the similarity in specific contact resistances.

Journal of Applied Physics

“…Furthermore, plasma damages resulted from plasma etching, a typical step during the fabrication of DUV devices, may act as deep-level compensation centers, thus make it even more difficult to form Ohmic contacts. Extensive studies have been performed regarding the Ohmic contacts to the non-plasma etched n-type AlGaN, and different metallization schemes in addition to the traditional titanium-based schemes [5][6][7] were proposed and demonstrated, such as vanadium-based schemes. [8][9][10] However, only few investigations on the formation of Ohmic contacts to plasma etched n-Al x Ga 1-x N (x > 0.4) have been reported and contradictory conclusions have been drawn.…”

mentioning

confidence: 99%

Improved Ohmic contacts to plasma etched n-Al0.5Ga0.5N by annealing under nitrogen ambient before metal deposition

Zhang

et al. 2013

The contact characteristics of Ti/Al and Ti/Al/Ni/Au contacts to as-grown, plasma etched and plasma etched + annealed in N2 n-Al0.5Ga0.5N epilayers were compared. After a rapid thermal annealing, both Ti/Al and Ti/Al/Ni/Au contacts to as-grown and plasma etched + annealed in N2 n-Al0.5Ga0.5N became truly Ohmic, whereas the contacts to plasma etched samples still remained rectifying. Surface atomic concentration analysis indicates the N vacancies resulting from plasma treatment act more as deep-level states rather than shallow donors. However, these deep-level states could be effectively removed by annealing the plasma etched n-Al0.5Ga0.5N under N2 ambient, and as a result, the Fermi level was elevated toward conduction band edge, facilitating the formation of Ohmic contacts.