The effect of Auger heating on intraband carrier relaxation in semiconductor quantumrods

The rate at which excited charge carriers relax to their equilibrium state affects many aspects of the performance of nanoscale devices, including switching speed, carrier mobility and luminescent efficiency. Better understanding of the processes that govern carrier relaxation therefore has important technological implications. A significant increase in carrier-carrier interactions caused by strong spatial confinement of electronic excitations in semiconductor nanostructures leads to a considerable enhancement of Auger effects, which can further result in unusual, Auger-process-controlled recombination and energy-relaxation regimes. Here, we report the first experimental observation of efficient Auger heating in CdSe quantum rods at high pump intensities, leading to a strong reduction of carrier cooling rates. In this regime, the carrier temperature is determined by the balance between energy outflow through phonon emission and energy inflow because of Auger heating. This equilibrium results in peculiar carrier cooling dynamics that closely correlate with recombination dynamics, an effect never before seen in bulk or nanoscale semiconductors.Comment: 7 pages, 4 figure

Interplay of bimolecular and Auger recombination in photoexcited carrier dynamics in silicon nanocrystal/silicon dioxide superlattices

Abstract We report results of investigating carrier recombination in silicon nanocrystal/silicon dioxide superlattices. The superlattices prepared by nitrogen-free plasma enhanced chemical vapour deposition contained layers of silicon nanocrystals. Femtosecond transient transmission optical spectroscopy was used to monitor carrier mechanisms in the samples. The three-particle Auger recombination was observed in accord with previous reports. However, under high pump intensities (high photoexcited carrier densities) the bimolecular process dominated the recombination. Detailed analysis of measured data and fitting procedure made it possible to follow and quantify the interplay between the two recombination processes. The bimolecular recombination was interpreted in terms of the trap-assisted Auger recombination

Advances and prospects of lasers developed from colloidal semiconductor nanostructures

Since the first observation of stimulated emission from colloidal quantum dots (CQDs) in year 2000, tremendous progress has been made in developing solution-processed lasers from colloidal semiconductor nanostructures in terms of both understanding the fundamental physics and improving the device performance. In this review paper, we will start with a brief introduction about the fabrication of CQDs and the corresponding electronic structures. The emphasis will be put on the discussion about the optical gain and lasing from colloidal nanostructures including the gain mechanism, the main hurdles against optical gain and lasing as well as strategies to optimize the lasing performance. Afterwards, the recent advances in CQD lasers, exemplified by the achievement of continuous wave lasing, will be presented. Finally, the challenges and a perspective of the future development of lasers based on the colloidal semiconductor nanostructures will be presented.MOE (Min. of Education, S’pore)Accepted versio