[Paper Review] Exact method of determination of the recombination mode from time resolved photoluminescence data

Paweł Strąk, Kamil Koroński+8 more|arXiv (Cornell University)|Sep 15, 2017

Spectroscopy and Laser Applications43 references3 citations

TL;DR

This paper presents an exact analytical method to determine the dominant recombination mechanism—monomolecular, bimolecular, or trimolecular—from time-resolved photoluminescence decay data. By fitting the decay kinetics to a generalized rate equation model, the method distinguishes between recombination orders and confirms that in III-nitride multi-quantum wells, monomolecular and bimolecular processes dominate, with negligible contribution from Auger recombination (trimolecular).

ABSTRACT

A method of data analysis is proposed for the determination of the carrier recombination processes in optically excited matter measured by time-resolved photoluminescence, differentiating monomolecular, bi-molecular, tri-molecular, and higher order molecular processes. Our method allows to determine whether the so-called ABC model describes time evolution of optical relaxation of the excited system. The procedure is applicable to the time evolution of any optically excited medium. As an illustration, the method is successfully applied to III-nitride polar and non-polar multi-quantum wells. We show that in this case the mono- and bi-molecular processes determine the carrier relaxation, and the tri-molecular Auger recombination contribution is negligible.

Motivation & Objective

• To develop a rigorous, exact method for identifying the recombination order (monomolecular, bimolecular, trimolecular, etc.) from time-resolved photoluminescence decay traces.
• To address the ambiguity in existing fitting methods that often assume a priori the form of decay kinetics without validating the underlying recombination model.
• To provide a general analytical framework applicable to any optically excited semiconductor system, regardless of material class or dimensionality.
• To test the validity of the widely used ABC model in describing carrier recombination dynamics in III-nitride multi-quantum wells.
• To quantitatively assess the contribution of Auger recombination (trimolecular process) in polar and non-polar InGaN/GaN multi-quantum wells.

Proposed method

• The method is based on solving a generalized rate equation for carrier density that includes terms for monomolecular (first-order), bimolecular (second-order), and trimolecular (third-order) recombination processes.
• It employs a nonlinear least-squares fitting procedure to time-resolved photoluminescence decay data, using the full analytical solution of the rate equation as the fitting function.
• The procedure evaluates the statistical significance of each recombination order by comparing the goodness of fit across models with increasing complexity (e.g., monomolecular only, up to ABC model).
• The method distinguishes between recombination mechanisms by analyzing the time dependence of the normalized decay curves and their derivatives.
• It uses a systematic model selection approach to determine whether the ABC model (including all three recombination channels) provides a significantly better fit than simpler models.
• The approach is validated using experimental data from both polar and non-polar InGaN/GaN multi-quantum wells, ensuring applicability across different material systems.

Experimental results

Research questions

• RQ1 Can an exact analytical method be developed to distinguish between monomolecular, bimolecular, and trimolecular recombination processes from time-resolved photoluminescence decay data?
• RQ2 Does the ABC model accurately describe the carrier recombination dynamics in III-nitride multi-quantum wells, particularly in non-polar structures?
• RQ3 What is the relative contribution of Auger recombination (trimolecular process) to the overall carrier decay in InGaN/GaN multi-quantum wells?
• RQ4 How does the proposed method improve upon conventional fitting techniques that rely on empirical decay laws without physical justification?
• RQ5 To what extent do monomolecular and bimolecular processes dominate the relaxation of photoexcited carriers in III-nitride semiconductors?

Key findings

• The proposed method successfully identifies the dominant recombination mechanisms in time-resolved photoluminescence data with high accuracy and physical consistency.
• For both polar and non-polar InGaN/GaN multi-quantum wells, the data are best described by a model that includes monomolecular and bimolecular recombination, with no significant contribution from trimolecular (Auger) recombination.
• The fitting results show that the Auger recombination coefficient is negligible in the studied systems, indicating that Auger processes do not significantly affect carrier lifetime in these materials under the measured conditions.
• The method demonstrates superior reliability compared to conventional fitting approaches that assume functional forms without validating the underlying physical model.
• The analysis confirms that the ABC model is not necessary for describing the decay dynamics in the studied III-nitride structures, as simpler models with only first- and second-order terms provide adequate fits.
• The approach enables unambiguous assignment of recombination mechanisms, reducing ambiguity in interpreting photoluminescence decay kinetics in optoelectronic materials.