TAYLORING OF THE SCHOTTKY-BARRIER HEIGHT OF PT-IR MIXED SILICIDE INFRARED DETECTORS

Pt-Ir silicide Schottky diodes were formed by e-beam evaporation of Pt and Ir onto p-Si(100) substrates in high vacuum with subsequent RTA-a nnealing at temperatures in the range of 300 to 500 degrees C. Rutherf ord Backscattering Spectrometry (RBS) and infrared photoresponse (PR) measurements were performed to determine the composition and the infra red electrooptical properties of the resulting films. Coevaporated Pt- Ir films are demixed during silicidation and form a PtSi layer at the interface to the silicon substrate. The Schottky barrier height is tha t of a pure PtSi film. Ir deposited prior to Pt exhibits Pt diffusion through the Ir layer. Only when the Ir film is reacted to IrSi by in s itu annealing prior to Pt deposition, a mixed Ir-Pt silicide Schottky barrier is obtained. Infrared photoemission then yields intermediate S chottky barrier heights between those of PtSi and IrSi. From a detaile d analysis of the photoemission characteristics, it is concluded that the intermediate barrier height is due to an area average of PtSi and IrSi grains which coexist at the Si interface.