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Improvement on Ti/Al/Ni/Au Electrical Contacts on GaN/AlGaN Superlattices

Improvement on Ti/Al/Ni/Au Electrical Contacts on GaN/AlGaN Superlattices. ___________________________________________________________ Tzu-Yung Huang 1, , Yu Song 1 , Rajaram Bhat 2 , Chung-En Zah 2 , and Claire F. Gmachl 1

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Improvement on Ti/Al/Ni/Au Electrical Contacts on GaN/AlGaN Superlattices

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  1. Improvement on Ti/Al/Ni/Au Electrical Contacts on GaN/AlGaN Superlattices ___________________________________________________________ Tzu-Yung Huang1,, Yu Song1, Rajaram Bhat2, Chung-En Zah2, and Claire F. Gmachl1 1 Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA 2 Corning Inc., Corning, NY 14831, USA Work supported by PEI Grand Challenges Program

  2. Improvement on Ti/Al/Ni/Au Electrical Contacts on GaN/AlGaN Superlattices ___________________________________________________________ • Quantum Cascade Lasers are used widely in trace gas sensing applications • III-Nitride materials have potential to achieve QCLs with emission wavelengths below 3µm, opening us up to a wider range of chemicals (C-H stretch vibration)

  3. Improvement on Ti/Al/Ni/Au Electrical Contacts on GaN/AlGaN Superlattices ___________________________________________________________ • So far, the overall high electrical resistance causes the device to heat up, precluding any emission • We tried several recipes varying Titanium thickness while keeping Al/Ni/Au overlay thickness constant, and found the best results at 6nm (25Ω) • We also optimized the annealing recipe, having the best results at 800°C for 80s

  4. Improvement on Ti/Al/Ni/Au Electrical Contacts on GaN/AlGaN Superlattices ___________________________________________________________ Ti 6nm ----- Ti10nm----- Ti40nm----- A B C D E F G -But hold on, are we sure that all of that is from the electrical contacts?

  5. Improvement on Ti/Al/Ni/Au Electrical Contacts on GaN/AlGaN Superlattices ___________________________________________________________ • To answer our question: we varied the gap distance between the outer and inner contact as well as the contact size • What we found: the average sheet resistance is 748.5Ω! While the specific contact resistivity is only 2.87e-4Ω • Our metal contacts weren’t the main culprit! Now we can make a new emitter sample with a new design Different contact sizes with varying gap spacing Rsh: 842.15Ω ρc: 3.43e-4Ω Corrected Total Resistance vs. Gap Distance for inner contact size 400 µm

  6. Improvement on Ti/Al/Ni/Au Electrical Contacts on GaN/AlGaN Superlattices ___________________________________________________________ Summary • Discover source of high device resistance • Measured sheet and specific contact resistance Conclusion • Extensive work experience in the clean room • Further understanding of Quantum Cascade Lasers and other related semiconductor devices that can be used for environmental applications • Results presented at MIRTHE Summer Workshop • Co-Author of conference paper to ITQW 2013 • Will co-author journal publication • Continuation of the project during the school year • Provided insights into post graduation plans

  7. Improvement on Ti/Al/Ni/Au Electrical Contacts on GaN/AlGaN Superlattices ___________________________________________________________ Thank You!

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