Field-driven attosecond photoinjection dynamics in semiconductors

TL;DR

This study uses attosecond transient reflection spectroscopy and theoretical analysis to unravel the complex ultrafast photoinjection dynamics in germanium, highlighting the influence of intra-band effects and pulse shape on charge injection.

Contribution

It provides a detailed, time-resolved understanding of charge photoinjection in semiconductors, emphasizing the role of intra-band phenomena and pulse envelope in controlling ultrafast carrier dynamics.

Findings

Intra-band phenomena hinder charge injection in germanium.

The pulse temporal envelope significantly affects photoinjection efficiency.

Disentangling physical processes at different reciprocal space points was achieved.

Abstract

The route towards manipulation of the optoelectronic properties of matter beyond the current limits of electronics starts from a comprehensive study of the ultrafast dynamics triggered by interaction with light. Among them, a fundamental role is played by charge photoinjection, a complex process that stems from the interplay of many different physical phenomena, which cannot be easily disentangled. Single- and multi-photon absorption, diabatic tunnelling, intra-band motion, and field-driven band dressing, all concur in determining the overall excited electron population, dictating the electro-optical properties of a material. Here we investigate ultrafast photoinjection in a prototypical semiconductor (monocrystalline germanium) by using attosecond transient reflection spectroscopy. The precise pump-field characterization ensured by a simultaneous attosecond streaking experiment, in tandem with a comprehensive theoretical approach, allowed us to disentangle the different physical phenomena unfolding at different positions in the reciprocal space and at different timing within the envelope of the pump pulse. Moreover, we found that intra-band phenomena hinder charge injection, in contrast to what was previously observed for resonant, direct band-gap semiconductors. Therefore, besides other known parameters as the central wavelength and peak intensity, our results indicate that the pulse temporal envelope and the local band structure probed by intra-band effects are of key importance to achieve an optimal control over the ultrafast carrier injection process and tailor the complex optical and electronic properties of a semiconductor on the few- to sub-femtosecond time scale.