Determination of the dependence of long-lived hot-carrier temperature on excitation power and its effect on the radiative decay rate in GaN/InGaN nanodisks

Abstract

Quantum-confined GaN/InGaN-based heterostructures are a natural choice for light-emitting devices due to their enhanced luminescence and superior efficiency. The reduced density of states and improved quantum confinement lead to improved radiative efficiency. However, under high excitation, quantum-confined structures exhibit band tail filling at elevated energies, giving rise to several effects, including altered carrier capture dynamics, extended radiative lifetimes, hot-carrier accumulation, and phonon bottlenecks. These effects may reduce the efficacy of the radiative process in the active region. Here, we show that the persistence of hot carriers—characterized by their elevated effective temperature and cooling dynamics—serves as a good metric for evaluating the overall efficacy of quantum-confined structures. To demonstrate this, we employ GaN/InGaN nanodisks as the host material and present a methodology for extracting hot-carrier temperature and cooling behavior using power-dependent photoluminescence and time-correlated single-photon counting measurements. While the radiative efficiency is measured around the peak emission wavelength, the short-wavelength tail reveals clear signatures of high-energy carrier occupation in both ground and excited states.