Cooling of photoexcited carriers in graphene by internal and substrate phonons

TL;DR

This paper studies how hot carriers in graphene cool down through interactions with both intrinsic and substrate phonons, highlighting the dominant role of substrate phonons and implications for optoelectronic device efficiency.

Contribution

It provides a detailed analysis of energy relaxation mechanisms in graphene, emphasizing the impact of substrate phonons on hot carrier cooling and device performance.

Findings

Remote substrate phonons dominate energy relaxation in graphene.

Calculated transient cooling times and steady-state carrier temperatures.

Substrate engineering can enhance optoelectronic device efficiency.

Abstract

We investigate the energy relaxation of hot carriers produced by photoexcitation of graphene through coupling to both intrinsic and remote (substrate) surface polar phonons using the Boltzmann equation approach. We find that the energy relaxation of hot photocarriers in graphene on commonly used polar substrates, under most conditions, is dominated by remote surface polar phonons. We also calculate key characteristics of the energy relaxation process, such as the transient cooling time and steady state carrier temperatures and photocarriers densities, which determine the thermoelectric and photovoltaic photoresponse, respectively. Substrate engineering can be a promising route to efficient optoelectronic devices driven by hot carrier dynamics.