Effect of silicon delta-doping density on optical properties of type-II InAs/GaAsSb quantum dots

We have investigated the optical properties of type-II InAs/GaAs_0.83Sb_0.17 quantum dots (QDs) with different silicon delta-doping densities of 5 × 10¹⁰, 5 × 10¹¹, and 2 × 10¹² cm^-2 using photoluminescence (PL). The PL spectra of the QD ground state (GS) emission peaks for the samples are blueshifted at a slower rate with increasing the doping density due to the enhanced radiative recombination rate of the carriers. The PL intensity ratio of the GS emission to the first excited state emission increases with the doping density, which is indicative of the faster radiative recombination at the GS subbands with the doping density. The redshift rate of the GS emissions becomes faster at a high temperature (>130 K) as the doping density increases up to 5 × 10¹¹ cm^-2 resulting from the quantum confined Stark effect by the electric field of the ionized dopants, and decreases at an increased doping density of 2 × 10¹² cm^-2 due to the enhanced QD size uniformity. Time-resolved PL exhibits that the QD sample doped at 5 × 10¹⁰ cm^-2 has a longer total radiative lifetime than the undoped sample, and a further increase in the doping density to 2 × 10¹² cm^-2 decreases the lifetime due to the enhancement of the radiative recombination through fast carrier relaxation.