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Electrical properties, microstructure, and thermal stability of Ta-based ohmic contacts annealed at low temperature for GaN HEMTs

Anna Malmros (Institutionen för mikroteknologi och nanovetenskap, Mikrovågselektronik) ; H. Blanck ; Niklas Rorsman (Institutionen för mikroteknologi och nanovetenskap, Mikrovågselektronik)
Semiconductor Science and Technology (0268-1242). Vol. 26 (2011), 7,
[Artikel, refereegranskad vetenskaplig]

Ta-based ohmic contacts to gallium nitride high electron mobility transistor (GaN HEMT) epitaxial structures were investigated. Two metallization schemes were considered: Ta/Al/Ni(Ta)/Au and Ta/Al/Ta. The latter was superior in terms of lower contact resistance (R-c) and wider process window. The metallizations were applied to two different heterostructures (GaN/Al0.14Ga0.86N/GaN and Al0.25Ga0.75N/GaN). The lowest measured R-c was 0.06 and 0.28 Omega mm, respectively. The main advantage of the Ta-based ohmic contacts over conventional Ti-based contacts was the low anneal temperature. The optimum temperature of annealing was found to be 550-575 degrees C. From optical and scanning electron microscopy, it was clear that excellent surface morphology and edge acuity were obtained at these low temperatures. This facilitates lateral scaling of the GaN HEMT. TEM images were taken of the contact cross sections onto which EDX measurements were performed. The aim was to investigate the microstructure and the contact mechanism. Storage tests at 300 degrees C for more than 400 h in air ambient showed no deterioration of R-c.

Nyckelord: field-effect transistors, mobility transistors, n-gan, algan/gan, resistance, heterostructures, microscopy

Denna post skapades 2011-05-05. Senast ändrad 2015-07-28.
CPL Pubid: 140346


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Institutioner (Chalmers)

Institutionen för mikroteknologi och nanovetenskap, Mikrovågselektronik


Elektroteknik och elektronik

Chalmers infrastruktur