Evidence for quantum confinement in the photoluminescence of porous Si and SiGe

Abstract

We have used anodization techniques to process porous surface regions in p-type Czochralski Si and in p-type Sio,ssGe,-,,s p e itaxial layers grown by molecular beam epitaxy. The SiGe layers were unrelaxed before processing. We have observed strong near-infrared and visible light emission from both systems. Analysis of the radiative and nonradiative recombination processes indicate that the emission is consistent with the decay of excitons localized in structures of one or zero dimensions.

Unusual Photoluminescence Decay of Porous Silicon Prepared by Rapid Thermal Oxidation and Quenching in Liquid Nitrogen

“…The blue shift of the PL peak by the rapid thermal oxidation (RTO) treatment can be 400 500 600 700 800 900 explained by a reduction in the average size of the silicon particles; as the nano-size silicon particles get smaller a widening of the band gap occurs, which leads to a blue shift of the PL. 1,[13][14][15][16] It is clear from Fig. 1 that the rapid quenching in liquid nitrogen causes no remarkable change in PL.…”

“…The former is based on the radiative recombination of quantum-confined electron-hole pairs across the wider band gap of silicon nano-particles. 1,[13][14][15][16] The latter claims various wide-gap surface species such as hydrogenated silicon, 2,[18][19][20] siloexene compounds, 3) silanone-based silicon oxyhydride, 21) and non-bridging oxygen hole center. 22,23) Furthermore, the local energy state at the silicon/SiO 2 interface [24][25][26] or at the silicon/SiO x interface 27,28) can lead to the blue PL of PS obtained through RTO.…”

Porous Silicon - New Luminescent Material or Luminescent Defect?

“…Typically, two kinds of decay characteristics are reported, for which decay times differ by three orders. The very "fast" decay is reported ranging from subnanoseconds to several nanoseconds, depending on temperature [12,13]. The most part of CW photoluminescence, however, corresponds to "slow" decay time ranging from several microseconds to some hundred microseconds at room temperature [14,15].…”

Photoresponse of Porous Silicon Structures to Infrared Radiation

“…These works served as a powerful breakthrough to the development of nanotechnology of porous silicon and to intensive research of silicon quantum structures, silicon quantum wires and silicon quantum dots, thus releasing from necessity to use technically more perfect but more expensive modern technologies. Strong stimulus for the investigations was discovery of changes of forbidden energy gap resulting in strong increase of radiating recombination efficiency in silicon quantum structures [3]. This opening released silicon from reputation of badly radiating semiconductor.…”