Biexciton Emission as a Probe of Auger Recombination in Individual Silicon Nanocrystals

Abstract

Biexciton emission from individual silicon nanocrystals was detected at room temperature by time-resolved, single-particle luminescence measurements. The efficiency of this process, however, was found to be very low, about 10−20 times less than the single exciton emission efficiency. It decreases even further at low temperature, explaining the lack of biexciton emission line observations in silicon nanocrystal single-dot spectroscopy under high excitation. The poor efficiency of the biexciton emission is attributed to the dominant nonradiative Auger process. Corresponding measured biexciton decay times then represent Auger lifetimes, and the values obtained here, from tens to hundreds of nanoseconds, reveal strong dot-to-dot variations, while the range compares well with recent calculations taking into account the resonant nature of the Auger process in semiconductor nanocrystals.

Single-dot absorption spectroscopy and theory of silicon nanocrystals

“…Previously we could access only the emission state of individual Si nanocrystals in photoluminescence [4,22] and decay measurements [15,23]. The Si quantum dot origin of the emission was evidenced by the observed variation in emission peak position and lifetime, the sharp narrowing of the linewidth at lowered temperature, a signature of biexciton recombination at high excitation, and a Si transverse optical (TO)-phonon sideband in the spectra.…”

Photothermally Activated Two-Photon Absorption in Ion-Implanted Silicon Quantum Dots in Silica Plates

“…Then, as the energy of the incident pulse increases, it is expected that a larger number of SiQDs with two excitons also increase until a saturated behavior is reached; this can explain the induced transparency observed in Figures 3 and 6 [21]. On the other hand, if the repetition rate of laser pulses is increased, two effects could take place: intraband absorption of electrons in the excited state [22] or biexciton emission [23] and both effects can explain the reduced transmittance of the SiQDs observed in this work. Biexciton deexcitation is a very inefficient process, but it is enhanced for higher temperatures and stronger laser intensities.…”

“…In Figure 8 representative self-diffraction signals obtained by a two-wave mixing experiment are shown; the repetition rate of the laser excitation was 10 Hz in this case. The nonzero value of the self-diffracted signal obtained by orthogonal polarization of the incident beams indicates an electronic mechanism as the main responsible for the optical Kerr effect induced in the sample by third-order nonlinearities [23]. The self-diffraction system was calibrated by using a well-known CS 2 standard sample.…”

Towards a Germanium and Silicon Laser: The History and the Present

“…A keen reader is referred to books dealing with Auger recombination in Si and Ge [38,39]. An interesting note in this context is the experimental observation of two radiative channels competing with Auger recombination, namely the light emission of a biexciton and of a trion, using single-nanocrystal spectroscopy in SiQDs [40,41]. These hint towards the possibility of lowered Auger rates in this material.…”