THERMOSTABLE TI AU/PT/TI SCHOTTKY CONTACTS TO N-TYPE 4H-SIC/

The electrical properties and interface chemistry of Ti/Au/Pt/Ti Schot tky contacts to n-type 4H-SiC have been investigated with respect to t heir utilization for MESFETs operated at high temperatures. The electr ical properties of these contacts were studied at room temperature as well as during thermal treatment. The barrier height determined from I -V characteristics was calculated to be 1.17 eV with an ideality facto r of 1.09. These parameters were examined by ageing and temperature de pendence tests as criteria for the thermal stability and reliability o f the contacts. The barrier height and ideality factor did not change after prolonged heating at a constant temperature of 500 degrees C and operating temperatures up to 350 degrees C, which confirmed the conta ct stability. Diodes used in the measurements showed a low leakage cur rent at 100 V reverse voltage and room temperature (2.48 x 10(-9) A) a s well as at 350 degrees C (2.15 x 10(-5) A) and breakdown voltage abo ve 400 V. The chemical interface properties were studied by x-ray phot oelectron spectroscopy for as-deposited, annealed and heated contacts. Annealing at 575 degrees C for 10 min led to formation of TIC and Pt, Si in a restricted region close to the SIC interface. The data reveale d a chemically stable Ti/SiC interface after annealing, which is of im portance for stable rectifying characteristics during long-term operat ion.