Ti/Al Ohmic Contacts to n-Type GaN Nanowires

Abstract

Titanium/aluminum ohmic contacts to tapered n-type GaN nanowires with triangular cross-sections were studied. To extract the specific contact resistance, the commonly used transmission line model was adapted to the particular nanowire geometry. The most Al-rich composition of the contact provided a low specific contact resistance (mid10−8 Ωcm2) upon annealing at 600 °Cfor 15 s, but it exhibited poor thermal stability due to oxidation of excess elemental Al remaining after annealing, as revealed by transmission electron microscopy. On the other hand, less Al-rich contacts required higher annealing temperatures (850 or 900 °C) to reach a minimum specific contact resistance but exhibited better thermal stability. A spread in the specific contact resistance from contact to contact was tentatively attributed to the different facets that were contacted on the GaN nanowires with a triangular cross-section.

Electrothermal phenomena in zinc oxide nanowires and contacts

“…Electrothermal transport data for relevant materials are examined to assess the impact of relative heating on an array of nanowire devices proposed for energy conversion applications. Figure 4.2 shows the relative heating versus specific contact resistivity for silicon [36,[44][45][46][47][48], gallium nitride [38,[49][50][51][52], and zinc oxide [2,[53][54][55]. Using data reported by previous studies, the relative heat generation rate is determined assuming typical metal-nanowire contact length, nanowire length, and device current of 1 µm, 10 µm, and 1 µA, respectively.…”