Electroluminescence and carrier transport in LEDs based on silicon-rich silicon oxide

LEDs based on silicon-rich silicon oxide (SRSO) have been fabricated utilizing thermal oxidation of electrochemically etched c-Si and standard microelectronic processes including LPCVD, photolithography, ion implantation and metallization. The bipolar devices consist of heavily-doped polycrystalline Si, a transition layer made of oxidized mesoporous Si, an active SRSO layer (doped or intrinsic) and a crystalline Si substrate. The LED's electrical properties exhibit a low interface state density which is explained by the partial filling of the micropores within the transition layer by polycrystalline Si. The dominant carrier transport in SRSO is due to thermally-assisted tunneling at low fields and electric field-assisted (Fowler-Nordheim) tunneling at high fields. The electroluminescence (EL) is stable and the EL modulation is limited by the carrier transition time (not by the carrier lifetime) which explains the high modulation speed (≥ 10 MHz). We have fabricated a prototype alphanumeric 7-segment display with an isolated version of the LEDs and standard microelectronic processing techniques.