Strong impact of x-ray radiation associated with electron beam metallization of diamond devices

Electron-beam evaporation of metal contact is commonly used in the fabricat ion of semiconductor devices. We have observed that device irradiation by x -ray photons, which are generated by electrons striking the metal (titanium or gold) to be evaporated, has a strong impact on the characteristics of d iamond devices used for radiation detection. It results in an improvement o f the detector charge collection efficiency by a factor of 1.5 with respect to nonirradiated devices (standard thermal evaporation). Thermally stimula ted current measurements showed that this effect is related to deep trap fi lling by free carriers generated in diamond by x-ray photons impinging the device during e-beam evaporation. Trap filling results in an increase of th e free carrier drift distance before trapping. Study of contact annealing a nd the thermal stability of trap filling showed that charge detrapping at t emperatures above 200 degreesC annihilates the observed detector sensitivit y improvement. (C) 2001 American Institute of Physics.