Ultrafast photocarrier relaxation processes in Er-doped InAs quantum dots embedded in strain-relaxed InGaAs barriers

• Published in: Journal of crystal growth 2013-09, Vol.378, p.485-488
• Main Authors: Kitada, Takahiro, Ueyama, Hyuga, Morita, Ken, Isu, Toshiro
• Format: Article
• Language: English
• Subjects: A1. Nanostructures; A3. Molecular beam epitaxy; B2. Semiconducting III–V materials; B3. Nonlinear optical; Barriers; Cross-disciplinary physics: materials science; rheology; Decay; Exact sciences and technology; Excitation; Indium arsenides; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Molecular, atomic, ion, and chemical beam epitaxy; Nanoscale materials and structures: fabrication and characterization; Other topics in nanoscale materials and structures; Physics; Quantum dots; Radiative recombination; Wavelengths
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2012.11.005

Time-resolved transmission change of Er-doped InAs quantum dots (QDs) embedded in strain-relaxed In0.45Ga0.55As barriers has been studied using different excitation wavelengths (1.4–1.55μm) to understand the QD-size dependence of the photocarrier relaxation. Each measured temporal profile was well reproduced by a sum of three exponential decays. Ultrafast (∼1.6ps) and fast (∼6–9ps) components are dominant in the initial stage of decay, and then the slow (∼70–130ps) component due to the radiative recombination in the QDs appears to be seen. The first two components come from photocarrier relaxation into the nonradiative centers related to Er dopants or the lattice relaxation. The difference is considered to result from whether the nonradiative centers are positioned inside or outside the QDs. The decay time for the outside case becomes shorter as the excitation wavelength is shortened, which might be due to the weaker confinement of photocarriers in the smaller-size QDs. Suppression of the QDs contributing to the radiative recombination is also more significant for the smaller-size QD excitation. ► We studied photocarrier decay in Er-doped InAs QDs with strain-relaxed barriers. ► Excitation wavelength dependence was measured to clarify the QD-size dependence. ► Ultrafast and fast decay components were observed due to nonradiative processes. ► Small-size Er-doped QDs are favorable for ultrafast all-optical devices.