Quantitative Assessment of Carrier Density by Cathodoluminescence. I. GaAs thin films and modeling

TL;DR

This paper presents a contactless, high-resolution cathodoluminescence method for quantitatively measuring carrier densities in GaAs thin films, enabling detailed doping analysis and potential mapping in nanostructures.

Contribution

It introduces a rigorous spectral fitting approach using CL to accurately determine doping levels and Fermi energy in GaAs, advancing non-invasive semiconductor characterization.

Findings

Validated the method over a wide doping range

Extracted bandgap narrowing and band tail parameters

Demonstrated potential for doping mapping in nanostructures

Abstract

Doping is a fundamental property of semiconductors and constitutes the basis of modern microelectronic and optoelectronic devices. Their miniaturization requires contactless characterization of doping with nanometer scale resolution. Here, we use low- and room-temperature cathodoluminescence (CL) measurements to analyze p-type and n-type GaAs thin films over a wide range of carrier densities ($2\times 10^{17}$ to $1\times 10^{19}$ cm$^{-3}$). The spectral shift and broadening of CL spectra induced by shallow dopant states and band filling are the signature doping. We fit the whole spectral lineshapes with the generalized Planck's law and refined absorption models to extract the bandgap narrowing (BGN) and the band tail for both doping types, and the electron Fermi level for n doping. This work provides a rigorous method for the quantitative assessment of p-type and n-type carrier density using CL. Taking advantage of the high spatial resolution of CL, it can be used to map the doping in GaAs nanostructures, and it could be extended to other semiconductor materials.