A STUDY OF SURFACE MODIFICATION AT SEMICONDUCTING GA2O3 THIN-FILM SENSORS FOR ENHANCEMENT OF THE SENSITIVITY AND SELECTIVITY

N-type semiconducting Ga2O3 thin films which are stable at high temper atures are being used as a new basic material for gas sensors. This st udy is an attempt to determine to what extent coating the surface of G a2O3 thin films with another metal oxide will produce new gas sensitiv ities. The process involves sputtering a modification layer which is t ypically 30-300 nm thick onto a readily prepared planar Ga2O3 sensor w ith a film thickness of 2 mu m Ta2O5, WO3, NiO and AlVO4 were used to form the modification layer. It was found that in some cases there was a radical change in gas sensitivity characteristics especially with W O3, NiO and AlVO4. The observed effects depend strongly on annealing a nd operating temperature. These results are the basis for sensors whic h react sensitively to NO and NH3, for selective O-2 sensors, for Ga2O 3 sensors which react to reducing gases with the same sign of conducti ng change as p-type semiconductors and a gas-sensitive reference eleme nt.