Photon statistics of incoherent cathodoluminescence with continuous and pulsed electron beams

TL;DR

This paper presents an analytical model for photon bunching in incoherent cathodoluminescence, relating it to electron excitation parameters, and validates it with experiments on quantum wells using various electron beam types.

Contribution

It introduces a fully analytical model for $g^{(2)}(\tau)$ in cathodoluminescence, extending analysis to ultrashort electron pulses and providing experimental validation.

Findings

Good agreement between model and experimental data.

Extracted excitation efficiencies of 0.13 and 0.05 for 10 and 8 keV beams.

Non-linear effects are negligible even with ultrashort dense electron pulses.

Abstract

Photon bunching in incoherent cathodoluminescence (CL) spectroscopy originates from the fact that a single high-energy electron can generate multiple photons when interacting with a material, thus revealing key properties of electron-matter excitation. Contrary to previous works based on Monte-Carlo modelling, here we present a fully analytical model describing the amplitude and shape of the second order autocorrelation function ($g^{(2)}(\tau)$) for continuous and pulsed electron beams. Moreover, we extend the analysis of photon bunching to ultrashort electron pulses, in which up to 500 electrons per pulse excite the sample within a few picoseconds. We obtain a simple equation relating the bunching strength ($g^{(2)}(0)$ to the electron excitation efficiency ($\gamma$), electron beam current, emitter decay lifetime and pulse duration, in the case of pulsed electron beams. The analytical model shows good agreement with experimental data obtained on InGaN/GaN quantum wells using continuous, ns-pulsed (using beam blanker) and ultrashort ps-pulsed (using photoemission) electron beams. We extract excitation efficiencies of 0.13 and 0.05 for 10 and 8 keV electron beams, respectively, and we observe that non-linear effects play no compelling role even after excitation with ultrashort and dense electron cascades in the quantum wells.