1. Time-resolved pump–probe spectroscopic ellipsometry of cubic GaN II: Absorption edge shift with gain and temperature effects.
- Author
-
Baron, Elias, Goldhahn, Rüdiger, Espinoza, Shirly, Zahradník, Martin, Rebarz, Mateusz, Andreasson, Jakob, Deppe, Michael, As, Donat J., and Feneberg, Martin
- Subjects
TEMPERATURE effect ,GALLIUM nitride ,ELLIPSOMETRY ,CONDUCTION bands ,DIELECTRIC function ,ION recombination - Abstract
We recently published a study concerning femtosecond pump–probe absorption edge spectroscopy of cubic GaN (fundamental bandgap: 3.23 eV), resulting in the transient dielectric function. In the present study, we continue our investigations of those pump–probe measurements by determining the time-dependent transition energy at the Fermi-vector between the conduction and valence bands. The generation of electron–hole pairs by the 266 nm pump-beam (4.66 eV) shifts the absorption edge by ≈ 500 meV within 1 ps due to many-body effects like band-filling and bandgap renormalization. Modeling this ultra-fast change is achieved by converting the transition energies into free-carrier concentrations, assuming the electron contributions to be dominant. We consider the relaxation, recombination, and diffusion of those free-carriers as well as either an additional gain-recombination or temperature effects. This allows for describing the transition energies on short time scales. Both models yield similar values for the characteristic relaxation time (≈ 0.21 ps), recombination time (≈ 25 ps), and diffusion coefficient (≈ 1 cm 2 /s). [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF