PHOTOLUMINESCENCE DUE TO DEGENERATE ELECTRON-HOLE SYSTEM IN SILICON-ON-INSULATOR WAFERS UNDER ULTRAVIOLET-LIGHT EXCITATION

Photoluminescence (PL) spectroscopy has been used for characterization of silicon-on-insulator (SOI) wafers with SOI thickness of 75 nm fabr icated by separation by implanted oxygen (SIMOX) technique. While PL s ignals from the substrate were dominant under conventional visible lig ht excitation, a characteristic broad line was observed under ultravio let (UV) light excitation throughout our temperature range between 4.2 to 70 K, The spectral distribution of the characteristic line agreed with calculated shape using convolution of the occupied electron and h ole densities of states. This agreement can be regarded as strong evid ence for formation of degenerate electron-hole systems, electron-hole liquid and electron-hole plasma, in the SOI layer. The detection of lu minescence due to these systems allows us to suggest that relief of cr ystalline damage in the SOI layer induced by oxygen implantation and i mprovement of quality of interfaces between the SOI layer and oxide la yers are efficiently achieved in the present low dose SIMOX process wi th an internal thermal oxidation.