SILICON BASED LIGHT EMITTING DIODE

PHASE I WORK HAS RESULTED IN THE FABRICATION OF THE FIRST ALL-SOLID-STATE PN HETEROJUNCTION POROUS SI LED CAPABLE OF VISIBLE LIGHT EMISSION AT ROOM TEMPERATURE. A P-TYPE SI WAFER WAS ANODICALLY ETCHED IN AN ETHONIC HYDROFLURIC ACID SOLUTION TO FORM A POROUS SILICON SURFACE LAYER WITH NANOSTRUCTURE SI CRYSTALLITES (WIRES); THEN A PN HETEROJUNCTION DIODE WAS FABRICATED BY DEPOSITING A WIDE BAND GAP N-TYPE SEMICONDUCTOR, INDIUM-TIN-OXIDE (ITO), ONTO THE POROUS SILICON LAYER. VISIBLE ELECTROLUMINESCENCE WAS OBSERVED AND MEASURED ONLY WHEN A POSITIVE VOLTAGE WAS APPLIED TO THE SI ELECTRODE--NO LIGHT EMISSION WAS OBSERVED UNDER THE REVERSE BIAS CONDITION. IN PHASE I, WE HAVE ALSO PRODUCED ROOM-TEMPERATURE RED, ORANGE, YELLOW AND GREEN PHOTOLUMINESCENT POROUS SI AND SIGE LAYERS. FACTORS INFLUENCING THE EMISSION WAVELENGTH OF THE POROUS MATERIAL INCLUDE ANODIC ETCHING PROCESS PARAMETERS, SUCH AS CURRENT DENSITY AND SUBSTRATE RESISTIVITY, AS WELL AS CONCENTRATION OF GE IN THE SIGE ALLOYS. MONOLITHIC INTEGRATION OF SI-BASED LIGHT EMITTERS WITH SILICON IC'S ON THE SAME CHIP IS POTENTIALLY USEFUL FOR OPTICAL INTERCONNECT AND DISPLAY TECHNOLOGIES.