Ultrafast dynamics of electronic structure in InN thin film

TL;DR

This study investigates the ultrafast electronic dynamics in InN thin films using simultaneous transient transmission and reflectivity measurements, revealing rapid processes like optical bleaching, band filling, and complex recombination behaviors under intense laser pulses.

Contribution

The paper provides detailed insights into the ultrafast optical and electronic processes in InN, including the effects of electron-electron interactions on band edge recombination, which were not previously characterized.

Findings

Optical bleaching occurs within ~260 fs due to Pauli blocking.

Recombination times are approximately 60 fs and 250-400 fs for different processes.

Electron-electron interactions suppress band edge recombination and affect recovery dynamics.

Abstract

Simultaneous measurements of transient transmission and reflectivity were performed in the unintentionally doped InN film to reveal ultrafast optical bleaching and its recovery behavior under intense laser irradiation. The optical bleaching is attributed to Pauli blocking due to the occupation of photoexcited electrons at the probing energy level. The time constant for the transition from the excitation state to the conduction band edge is $\sim$260 fs. The interplay between band filling and band gap renormalization caused by electron-hole and electron-electron interactions gives rise to complex spectral characteristics of transient reflectivity, from which the time constants of photoexcited electron-hole direct recombination and band edge recombination are extracted as $\sim$60 fs and 250$\sim$400 fs, respectively. Our results also reveal that the electron-electron interaction suppresses band edge recombination, and mitigates the recovery process. Our experiments highlight the controllability of the band structure of semiconductors by intense laser irradiation.