We studied the optical properties of InAs/GaAs_0.83Sb_0.17 quantum dots (QDs), with varying silicon delta-doping position (spatial distance, d = 0.5, 1, and 2 nm), using photoluminescence (PL) measurements. Compared with the undoped QDs, the PL peak energies of the ground state (GS) emissions for the doped QDs with d = 0.5 and 2 nm were found to be greatly blueshifted by ~31 meV, which was much larger than that for the doped QDs with d = 1 nm. The radiative recombination rate of the GS emissions for the doped QDs with d = 1 nm was estimated to be slower than that for the other doped QDs at 10 K. The doped QDs with d = 1 nm showed the fastest redshift of the GS peak energy with temperature and lowest thermal activation energy (151 meV) of electrons among the QD samples. Further, the time-resolved PL data revealed that the average carrier lifetime (6.3 ns) in the doped QDs with d = 1 nm was longer even than that in the undoped QDs (5.5 ns) because of the weakened electron-hole wavefunction overlap by the V-shaped potential barrier in the doped QDs.