Towards higher electron mobility in modulation doped GaAs/AlGaAs core shell nanowires

Towards higher electron mobility in modulation doped GaAs/AlGaAs core shell nanowires

Boland, Jessica L. (University of Oxford)
Tütüncüoglu, Gözde (Swiss Federal Institute of Technology)
Gong, Juliane Q. (University of Oxford)
Conesa Boj, S. (TU Delft QN/Conesa-Boj Lab; Kavli institute of nanoscience Delft)
Davies, Christopher L. (University of Oxford)
Herz, Laura M. (University of Oxford)
Fontcuberta Morral, Anna (Swiss Federal Institute of Technology)
Johnston, Michael B. (University of Oxford)

2017

Precise control over the electrical conductivity of semiconductor nanowires is a crucial prerequisite for implementation of these nanostructures into novel electronic and optoelectronic devices. Advances in our understanding of doping mechanisms in nanowires and their influence on electron mobility and radiative efficiency are urgently required. Here, we investigate the electronic properties of n-type modulation doped GaAs/AlGaAs nanowires via optical pump terahertz (THz) probe spectroscopy and photoluminescence spectroscopy over the temperature range 5 K-300 K. We directly determine an ionization energy of 6.7 ± 0.5 meV (T = 52 K) for the Si donors within the AlGaAs shell that create the modulation doping structure. We further elucidate the temperature dependence of the electron mobility, photoconductivity lifetime and radiative efficiency, and determine the charge-carrier scattering mechanisms that limit electron mobility. We show that below the donor ionization temperature, charge scattering is limited by interactions with interfaces, leading to an excellent electron mobility of 4360 ± 380 cm² V^-1 s^-1 at 5 K. Above the ionization temperature, polar scattering via longitudinal optical (LO) phonons dominates, leading to a room temperature mobility of 2220 ± 130 cm² V^-1 s^-1. In addition, we show that the Si donors effectively passivate interfacial trap states in the nanowires, leading to prolonged photoconductivity lifetimes with increasing temperature, accompanied by an enhanced radiative efficiency that exceeds 10% at room temperature.

http://resolver.tudelft.nl/uuid:2b41cb95-68cd-4d82-94a5-e4f8e344daaf

https://doi.org/10.1039/c7nr00680b

2040-3364

Nanoscale, 9 (23), 7839-7846

Institutional Repository

journal article

© 2017 Jessica L. Boland, Gözde Tütüncüoglu, Juliane Q. Gong, S. Conesa Boj, Christopher L. Davies, Laura M. Herz, Anna Fontcuberta Morral, Michael B. Johnston