Low Resistance, Thermally Stable Ohmic-Contacts to n-AlGaN
Lower resistance in ohmic-contacts have been attained on V/Al/Mo/Au with a contact resistance as low as 0.15 ohm-mm achieved when this ohmic-contact is annealed at 800° C for 30 sec. Mo/Al/Mo/Au and V/Al/Mo/Au have shown to have become ohmic at annealing temperatures as low as 650° C and 600° C respectively. These temperatures are much lower than that for Ti/Al/Mo/Au which is observed to have high resistance and low current saturation values when annealed even at 700° C and 750° C. The Ti/Al/Mo/Au metallization scheme forms low contact resistance ohmic-contacts on n-AlGaN that are stable at 500° C and 600° C after over 25 hrs of thermal treatment. The sample starts degrading when treated at 750° C for 10 hrs and at 850° C for only 1hr. SEM images have shown that Ti/Al/Mo/Au based contacts have a smooth morphology, while it was observed that Mo/Al/Mo/Au had slight roughness. V/Al/Mo/Au showed an even greater surface roughness and non-uniformity, especially around the edges. These characteristics could be attributed to the extent that these individual metallization schemes are prone to oxide formation.
School:
University of Illinois at Urbana-Champaign
Department:
Computer Engineering
Research Advisor:
Ilesanmi Adesida
Department of Research Advisor:
Electrical Engineering
Year of Publication:
2003