InN-based Ohmic contacts to InAlN

The ability to form low resistance Ohmic contacts to InAlN using refractory metallization on In-containing contact layers has been investigated. The crystal quality as measured by surface roughness and x-ray diffraction was found to be a determining factor in the contact resistance which could be obtained using WSix contacts. InN growth conditions which resulted in poorer structural quality, such as the use of GaAs rather than sapphire substrates, low nitrogen flows, and low growth temperatures, resulted in contact resistances of 10−4–10−3 Ω cm2, as compared to ∼10−5 cm2 for InAlN alone. Using optimized conditions, contact resistances to InAlN of ∼3.5×10−6 Ω cm2 were obtained.