Silicon light emission is a rapidly growing area of inquiry. This field is uniquely important due to the dependence on silicon in the modern microelectronics industry. To economically create optical interconnects and circuit elements, the development of a silicon-compatible light emitter is critical, and the last two decades have shown marked advancement in the field of silicon light emission. To develop novel low-cost silicon components, several groups have utilized the technology developed for complementary metal oxide semiconductor (CMOS) processing to design nanoscale structures. Low-dimensional structures, such as nanopillars or nanocrystals patterned with “top-down” techniques are examples of these efforts.
In this work, we fabricate top-down, ICP-RIE “Pseudo Bosch” etched, Si nanopillars and further thinned them via self-terminating oxidation to demonstrate photoluminescence as well as measure radiative lifetime with respect to reduction in pillar diameter. This work demonstrated that cylindrical silicon pillars exhibit a self-terminating core diameter and oxide thickness that is a function of the initial silicon diameter and the temperature of the oxidation.
We demonstrated room-temperature visible and near-IR photoluminescence (PL) from sub 10-nm nanopillars etched from wafers of single crystal silicon. Finite element strain modeling was used to calculate the radial and circumferential strain in the nanowires after oxidation. PL, charge carrier lifetime, and transmission electron microscopy were performed to measure the dimensions and emission characteristics of the pillars. The uniformity in pillar diameter has allowed us to investigate the role of pillar diameter as well as oxidation strain in determining the peak emission energy. The peak PL energy was found to blue shift with narrowing pillar diameter in accordance with a quantum confinement effect. This blue shift tuning agrees with previous experimental and was quantified using a tight binding method simulation that incorporated the strain induced by the thermal oxidation process. The fabrication process to create these pillars is fully CMOS-compatible and is a promising method to create integrated, visible and near-IR, on-chip silicon LED or laser devices.
- Walavalkar, S., Hofmann, C. E., Homyk, A., Henry, M. D., Atwater, H. A. & Scherer, A. (2010). Tunable Visible and Near-IR Emission from Sub-10nm Etched Single-Crystal Si Nanopillars. Nano Letters, 10(11), 4423-4428.