Doping effect on photocarrier lifetime in InAs quantum dots with strain-relaxed InGaAs barriers grown by molecular beam epitaxy

We have studied effects of Si and Be δ-dopingδ-doping on photocarrier lifetime in self-assembled InAs quantum dots (QDs) with strain-relaxed In0.35Ga0.65AsIn0.35Ga0.65As barriers grown on (1 0 0) GaAs substrates by molecular beam epitaxy. Relaxation of photocarriers generated in the QDs was characterized by time-resolved transmission change measurements at room temperature. Fast and slow decay components were observed in the temporal profile of each QD sample at an excitation wavelength of 1.5μm. A slow decay component attributed to the radiative recombination process in the QDs was rather suppressed by Be δ-dopingδ-doping after the QD formation. On the other hand, Si δ-dopingδ-doping resulted in shortening of the decay time of the fast component due to the nonradiative process arising from the crystal defects related to the lattice-mismatch. The decay time observed in the Si δ-dopedδ-doped QD sample was 9 ps, which was the half of those (18 ps) observed in the undoped and Be δ-dopedδ-doped QD samples.