Effect of thermal annealing on ohmic contacts properties of undoped and Si-doped AlxGa1-xN on Si (111) substrate grown by PA-MBE

In this work, we study the ohmic contact properties of titanium (Ti)/aluminum (Al) bi-layer contacts on undoped and n-type doped AL(x)Ga(1-x)N grown on silicon (1 1 1) substrates by radio frequency nitrogen plasma-assisted molecular beam epitaxy (PA-MBE). The electrical stability of the contacts at various annealing temperatures of 400, 500, 600 and 700 degrees C were investigated. Specific contact resistivity was determined using transmission line method (TLM) and current-voltage (I-V) measurements. The results reveal that the bi-layer scheme was sensitive to the change of annealing temperatures and annealing time. The optimal value of specific contact resistivities was obtained at annealing temperature of 600 degrees C for both samples. However, the values of n-type doped sample exhibited better results compared with the undoped sample. (c) 2013 Published by Elsevier GmbH.