Precise control of doping in single nanowires (NWs) is essential for the development of NW-based devices. Here, we investigate a series of MBE-grown GaAs NWs with Be (p-type) and Si (n-type) doping using high-resolution cathodoluminescence (CL) mapping at low- and room-temperature. CL spectra are analyzed selectively in different regions of the NWs. Room-temperature luminescence is fitted with the generalized Planck law and an absorption model, and the bandgap and band tail width are extracted. For Be-doped GaAs NWs, the bandgap narrowing provides a quantitative determination of the hole concentration ranging from about 1×1018 to 2×1019~cm−3, in good agreement with the targeted doping levels. High-resolution maps of the hole concentration demonstrate the homogeneous doping in the pure zinc-blende segment. For Si-doped GaAs NWs, the electron Fermi level and the full-width at half maximum of low-temperature CL spectra are used to assess the electron concentration to approximately 3×1017 to 6×1017~cm−3. These findings confirm the difficulty to obtain highly-doped n-type GaAs NWs, maybe due to doping compensation. Notably, signatures of high concentration (5--9×1018~cm−3) at the very top of NWs are unveiled.
@article{arxiv.1909.05602,
title = {Quantitative Assessment of Carrier Density by Cathodoluminescence. II. GaAs nanowires},
author = {Hung-Ling Chen and Romaric De Lépinau and Andrea Scaccabarozzi and Fabrice Oehler and Jean-Christophe Harmand and Andrea Cattoni and Stéphane Collin},
journal= {arXiv preprint arXiv:1909.05602},
year = {2022}
}