Carrier concentration dependent photoluminescence properties of Si-doped InAs nanowires

Abstract

We report the effects of intentional n-type doping on the photoluminescence (PL) properties of InAs nanowires (NWs). Employing silicon (Si) as a dopant in molecular beam epitaxy grown NWs, the n-type carrier concentration is tuned between 1 × 1017 cm−3 and 3 × 1018 cm−3 as evaluated from Fermi-tail fits of the high-energy spectral region. With the increasing carrier concentration, the PL spectra exhibit a distinct blueshift (up to ∼50 meV), ∼2–3-fold peak broadening, and a redshift of the low-energy tail, indicating both the Burstein-Moss shift and bandgap narrowing. The low-temperature bandgap energy (EG) decreases from ∼0.44 eV (n ∼ 1017 cm−3) to ∼0.41 eV (n ∼ 1018 cm−3), following a ΔEG ∼ n1/3 dependence. Simultaneously, the PL emission is quenched nearly 10-fold, while the pump-power dependent analysis of the integrated PL intensity evidences a typical 2/3-power-law scaling, indicative of non-radiative Auger recombination at high carrier concentrations. Carrier localization and activation at stacking defects are further observed in undoped InAs NWs by temperature-dependent measurements but are absent in Si-doped InAs NWs due to the increased Fermi energy.