Biexciton recombination rates in self-assembled quantum dots

Abstract

The radiative recombination rates of interacting electron-hole pairs in a quantum dot are strongly affected by quantum correlations among electrons and holes in the dot. Recent measurements of the biexciton recombination rate in single self-assembled quantum dots have found values spanning from two times the single exciton recombination rate to values well below the exciton decay rate. In this paper, a Feynman path-integral formulation is developed to calculate recombination rates including thermal and many-body effects. Using real-space Monte Carlo integration, the path-integral expressions for realistic three-dimensional models of InGaAs/GaAs, CdSe/ZnSe, and InP/InGaP dots are evaluated, including anisotropic effective masses. Depending on size, radiative rates of typical dots lie in the regime between strong and intermediate confinement. The results compare favorably to recent experiments and calculations on related dot systems. Configuration interaction calculations using uncorrelated basis sets are found to be severely limited in calculating decay rates.

Photoluminescence from a single InGaAs epitaxial quantum rod

“…In the strong confinement limit, the exciton to biexciton lifetime ratio is expected to be approximately 2 ͑explained by twice larger number of decay channels for biexciton͒ and should decrease significantly when going into the weak confinement regime. 8 There have been used X / XX = 2 in Fig. 4 as the first approximation ͑shown with dashed lines͒, which seems to describe our experimental result quite well.…”

“…Large X / XX ratios, which mean biexciton radiative lifetime significantly shorter than the exciton one, have been previously suggested in both theoretical predictions 8,10,11 and experimental reports 12,13 for different dots showing that they can occur under certain circumstances ͑geometries, contents, sizes, etc.͒. One of the fundamental reasons, proposed in a recent paper by Narvaez et al, 14 is related to the existence of the exciton fine structure ͑i.e., a splitting into two bright and two dark states caused by electron-hole exchange interaction͒.…”

“…The obtained binding energies are close to those previously observed and reported for typical selfassembled InAs or InGaAs quantum dots in GaAs host. 8,11,12,15 This can be understood taking into account that both the self-assembled dots and the quantum rods investigated here are in the strong confinement regime ͑even if at its large size limit͒. Indeed, in this range of sizes ͑volumes͒ a very weak dependence of the biexciton binding energy on the object size is expected 8,11 and can be fully dominated by other local ensemble properties.…”

Photoluminescence spectroscopy of trions in quantum dots: A theoretical description

“…[10][11][12][13][14][15][16][17][18][19][20][21][22][23] The dependence of the recombination rates of neutral exciton, biexciton, and multiexciton complexes on Coulomb interactions has been also described in a number of papers. [24][25][26][27][28][29][30] Much less is known about the recombination rates of positively ͑X + ͒ and negatively ͑X − ͒ charged excitons ͑trions͒. 20,31,32 This is nonetheless an interesting problem.…”

Progress in the optical studies of single InGaN/GaN quantum dots

“…The recombination dynamics of multi-excitonic states also reveal important information on the quantum correlations among electrons and holes localized in the QD [43]. This can be achieved through time-resolved measurements of the recombination rates for the different states.…”