Current-voltage characteristics of AlN/GaN heterostructure metal insulatorsemiconductor diode

We fabricated heterostructure metal insulator semiconductor (Hetero-MIS) di odes with a Schottky metal-(Ni/Au)/AlN(6 nm)/n(+)-GaN(Si:3 x 10(18) cm(-3)) /ohmic metal-(Ti/AL/Pt/Au) structure, and measured the dependence of curren t-voltage (I-V) characteristics of the diodes on the growth temperature of the AIN layer using low-pressure metalorganic chemical vapor deposition (MO CVD). We found that the current decreases as the growth temperature of the AIN layer decreases from 990 degreesC to 650 degreesC. We conclude that the current flows mainly between the columnar crystals of the AIN layer, becau se we found from the temperature dependence of the surface morphology of th e AIN layer that the radius of the columnar crystals decreases and the heig ht of the columns decreases as the growth temperature decreases, and becaus e the measured I-V characteristics are in agreement with the simulated ones if we assume that the thickness of the AIN layer is about 2 nm, which is m uch less than the measured thickness of the columnar crystal of 6 nm.