OPTICAL CHARACTERIZATION OF DIAMOND MIS CAPACITORS

The transient photoresponse properties of diamond metal-insulator-semi conductor (MIS) capacitors have been characterized for the first time. Capacitors were fabricated on natural diamond using an electrochemica l cleaning step with a CVD SiO2 dielectric and an optional carbon impl antation to create a nonuniform doping profile. Devices were found to function as integrating photodetectors and were evaluated bv the spect ral dependence of the transient photocapacitance (PC). We discuss a mo del that distinguishes between the responses due to inversion layer po pulation and that due to bulk trap occupancy changes. Inversion charge generation was observed at all wavelengths investigated and it domina ted the PC transient at photon energies above 3 eV. Possible reasons f or this result are discussed and analyzed. We could not demonstrate a suitable way to use carbon implantation to form a surface n-type layer in a MIS device without degrading the device IV properties and elimin ating the integrating photoresponse observed on non-implanted devices. These results suggest that diamond charge-storage devices can functio n only if the diamond surface is prepared properly before device fabri cation.