Determination of the effective carrier concentration in GaAs/AlGaAs core-shell nanowires using optical techniques

Determining the concentration of electrically active dopants in III-V core-shell nanowires has long been a problem due to the difficulty of forming ohmic contact with the nanowire core. In this letter, we have used a non-contact optical method to estimate the electron concentration in Si-doped GaAs:Si/Al0.25Ga0.75As core-shell nanowires. The temperature-dependent photoluminescence spectra of these GaAs:Si/Al0.25Ga0.75As nanowires indicate that at 15 K, the carrier concentration in the conductive core of the core-shell nanowires can be as high as 1.40×1018 cm-3. In order to accurately determine the concentration of carriers in the nanowires using optical methods, the band-filling effect was taken into account. The highest electron density is achieved for a nominal Si concentration of 1.90×1019 cm-3, and a further increase in Si concentration reduces the effective doping level due to the amphoteric behaviour of Si in GaAs. The dependence of the integrated photoluminescence intensity on the laser power at T = 15 K shows a typical 2/3 power dependence, indicating the presence of a non-radiative Auger recombination mechanism in the nanowire under high carrier concentration.