7 March 2005 Effects of post annealing treatments on the characteristics of ohmic contacts on n-type AlGaN
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In this work, we investigate the thermal stability and surface morphology of Ti metal contact on unintentionally doped n-type aluminum gallium nitride (AlGaN). Different annealing temperatures (400°C - 800°C) and durations (1 - 30 minutes) are investigated, as thermally stable metal-semiconductor contacts are essential for high quality devices. Cryogenic quenching after heat treatment is also performed to determine the effects of this treatment on the characteristics of the contacts. Specific contact resistivity, ρc (SCR) determined using transmission line method (TLM) and scanning electron microscopy (SEM) measurements are carried out to the as-deposited, annealed (A), and annealed-and-cryogenically (A+C) treated contacts where the electrical behavior and the surface morphology of each of these conditions are compared. The result shows that cryogenic treatment is able to reduce the SCRs after annealing as most of the A+C samples exhibited lower SCR as compared to A samples. For relatively low annealing temperatures, i.e. 500°C and below, the difference of SCR values between A and A+C treated samples is insignificant, however, when the samples are thermally treated at higher temperatures, i.e. 600°C and above, substantial difference of the SCR values is observed between A and A+C treated samples. SEM images indicate that little difference of surface morphology is observed for all the samples regardless of the annealing temperatures, durations and treatments. The A+C sample annealed at 600°C for 2 minutes is found to be able to yield the lowest SCR in this study.
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Zainuriah Hassan, Zainuriah Hassan, Fong Kwong Yam, Fong Kwong Yam, Yan Cheung Lee, Yan Cheung Lee, Surina Othman, Surina Othman, "Effects of post annealing treatments on the characteristics of ohmic contacts on n-type AlGaN", Proc. SPIE 5739, Light-Emitting Diodes: Research, Manufacturing, and Applications IX, (7 March 2005); doi: 10.1117/12.598717; https://doi.org/10.1117/12.598717


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