Direct Time-Domain View of Auger Recombination in a Semiconductor

Abstract

The radiationless recombination of electron-hole pairs in semiconductors is detrimental to optoelectronic technologies. A prominent mechanism is Auger recombination, in which nonradiative recombination occurs efficiently by transferring the released energy-momentum to a third charge carrier. Here we use femtosecond photoemission to directly detect Auger electrons as they scatter into energy and momentum spaces from Auger recombination in a model semiconductor, GaSb. The Auger rate is modulated by a coherent phonon mode at 2 THz, confirming phonon participation in momentum conservation. The commonly assumed Auger rate constant is found not to be a constant, but rather decreases by 4 orders of magnitude as hot electrons cool down by ∼90 meV. These findings provide quantitative guidance in understanding Auger recombination and in designing materials for efficient optoelectronics.

Multicarrier Dynamics in Quantum Dots

“…In p -type GaSb with a 0.72 eV gap, phonons have been experimentally implicated in the Auger recombination by transient photoemission measurements, showing a modulation of the detected Auger electron flux at a frequency consistent with a lattice vibration . The Auger coefficient in this material, however, is the subject of considerable uncertainty.…”

“…This method has become more common in recent years due to technical advances. Modern photoemission studies have on occasion prompted revisions of conventional wisdom established in the era of transport-dominated measurements, especially for materials with more complicated band structures. , Reliable measurements of Auger recombination rates in large-gap systems have often been limited by the fact that Auger recombination is slower at larger gaps and therefore competes with many other processes. Rather high carrier densities must then be used to make Auger recombination the dominant decay mechanism, and this can introduce experimental difficulties.…”

Auger Suppression in n-Type HgSe Colloidal Quantum Dots

“…The Auger mechanism is relatively well understood in bulk semiconductors. It is often calculated by application of perturbation theory, considering the screened Coulomb interactions between carriers under energy and momentum conservation. − For small-gap materials it is a direct process, ,, while phonons are required at larger energies. ,,, Due to the increasing ease of momentum conservation, the Auger rate grows rapidly in bulk materials as the energy gap decreases.…”

“…5−7 For small-gap materials it is a direct process, 5,6,8 while phonons are required at larger energies. 4,5,8,9 Due to the increasing ease of momentum conservation, the Auger rate grows rapidly in bulk materials as the energy gap decreases.…”

Suppression of the Auger Recombination Process in CdSe/CdS Core/Shell Nanocrystals

“…1−3 To date, various methods have been carried out to explore the geometry, shape, and surface carrier trap assistance effects on the AR process both theoretically 4−11 and experimentally. 12−19 In particular, compared with bare nanosolids, the core/shell nanostructures show a different AR process. 20 The epitaxial layer in the core/shell nanostructures can offer a new pathway to separate the electron and hole because the electron (or hole) may delocalize over the entire core/shell nanostructures.…”