A model for the temperature dependence of photoluminescence from self-assembled quantum dots

TL;DR

This paper introduces a simple, thermodynamic model to explain the unusual temperature-dependent photoluminescence behaviors observed in self-assembled quantum dots, including non-monotonic energy shifts and linewidth narrowing.

Contribution

It presents a novel quasi-thermodynamic model that uses a temperature-dependent parameter to describe carrier thermalization, simplifying analysis compared to traditional rate equation methods.

Findings

The model accurately reproduces anomalous PL spectra behaviors.

It reduces the number of fitting parameters needed for analysis.

The approach extends to quantum dots with size distributions.

Abstract

Photo-excited carriers, distributed among the localized states of self-assembled quantum dots, often show very anomalous temperature dependent photoluminescence characteristics. The temperature dependence of the peak emission energy may be non-monotonic and the emission linewidth can get narrower with increasing temperature. This paper describes a quasi-thermodynamic model that naturally explains these observations. Specifically, we introduce a temperature dependent function to parameterize the degree of thermalization of carriers. This function allows us to continuously interpolate between the well-defined low and high temperature limits of the carrier distribution function and describe the observed anomalies in the photoluminescence spectra with just two fitting parameters. We show that the description is equivalent to assuming that the partially thermalized carriers continue to be described by equilibrium statistics, but with a higher effective temperature. Our treatment of the problem is computationally simpler than the usually employed rate equations based analyses [e.g. Sanguinetti, et al. Phys. Rev. B 60, 8276 (1999)], which typically also have many more under-determined fitting parameters. The model is extended to quantum dots with a bimodal size distribution.