Gold-free contacts on Al x Ga 1-x N/GaN high electron mobility transistor structure grown on a 200-mm diameter Si(111) substrate

• Main Authors: Tham, Wai Hoe, Ang, Diing Shenp, Bera, Lakshmi Kanta, Surani Bin Doimanan, Bhat, Thirumaleshwara N., Kajen, Rasanayagam S., Tan, Hui Ru, Teo, Siew Lang, Tripathy, Sudhiranjan
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2018
• Subjects: Electrical Resistivity; DRNTU::Engineering::Electrical and electronic engineering; Aluminium
• Online Access: https://hdl.handle.net/10356/89018; http://hdl.handle.net/10220/47018
• Institution: Nanyang Technological University

The authors report on the fabrication and characterization of low-temperature processed gold-free Ohmic contacts for AlxGa1−xN/GaN high electron mobility transistors (HEMTs). The HEMT structure grown on a 200-mm diameter Si(111) substrate is used in this study. Using the Ti/Al/NiV metal stack scheme, the source/drain Ohmic contact optimization is accomplished through the variation of Ti/Al thickness ratio and thermal annealing conditions. For an optimized Ti/Al stack thickness (20/200 nm) annealed at 500 °C for 30 s with smooth contact surface morphology, a specific contact resistivity of ∼6.3 × 10−6 Ω cm2 is achieved. Furthermore, with gold-free Ni/Al gates, the fabricated HEMTs exhibit ION/IOFF ratio of ∼109 and a subthreshold swing of ∼71 mV/dec. The demonstrated gold-free contact schemes thus provide a solution toward the implementation of GaN-based HEMT process on a Si foundry platform.