Abstract
Ohmic contacts to polarization doped, compositionally graded indium gallium nitride (InGaN) films have been studied. The strong spontaneous and piezoelectric polarizations exhibited by the III-nitride materials result in effective doping in the graded layers without the use of impurity dopants. Two samples were grown by grading the In composition from-5% to 21.5% or 28% over 90 nm on top of GaN by molecular beam epitaxy, resulting in carrier concentrations of 2.13 x 1018 cm-3 and 2.87 x 1018 cm-3, respectively. Both films of Ni and Cr metals were tested for contact quality. Transmission line measurements demonstrated a minimum specific contact resistance of 3.19 x 10-4 0 cm2 resulting from room temperature deposition of Cr. The methods and materials characterization will be discussed.