An Instantaneous Recombination Rate Method for the Analysis of Interband Recombination Processes in ZnO Crystals

Area of Science:

• Materials Science
• Solid State Physics
• Semiconductor Physics

Background:

• Traditional time-resolved photoluminescence (TRPL) analysis often uses phenomenological fitting functions (e.g., multi-exponential decays) for semiconductor crystals.
• These methods yield parameters lacking direct physical significance, particularly for interband photoluminescence (PL) in direct gap semiconductors.
• A need exists for quantitative analysis of recombination dynamics in materials like zinc oxide (ZnO).

Purpose of the Study:

• To develop and validate a novel data analysis method for TRPL in ZnO bulk crystals.
• To demonstrate that TRPL decays in ZnO can be accurately described by second-order kinetics under specific laser excitation conditions.
• To extract fundamental physical quantities related to charge carrier recombination from experimental TRPL data.

Main Methods:

• Applying second-order kinetic analysis to the total recombination rate of ZnO bulk crystals.
• Evaluating the "instantaneous" recombination rate from the initial slope of TRPL decay curves as a function of excitation laser fluence.
• Fitting experimental data using the developed method to determine key recombination parameters.

Main Results:

• TRPL decays in ZnO bulk crystals are precisely described by second-order kinetics within a defined laser excitation range.
• The developed method successfully extracts fundamental physical quantities, including PL lifetime, bimolecular recombination coefficient, non-radiative lifetime, and equilibrium free-carrier concentration.
• The obtained results for ZnO are consistent with those typically observed in direct gap semiconductors.

Conclusions:

• A new, quantitative method for analyzing TRPL data in ZnO has been established, based on second-order recombination kinetics.
• This method offers valuable insights into charge carrier recombination processes and excitonic dynamics in ZnO.
• The approach provides a pathway to obtain fundamental physical quantities, enhancing the understanding of ZnO semiconductor behavior.