Modified self-assembly of InAs islands acting as stressors for strain-induced InGaAs(P)/InP quantum dots

Abstract

We report modified self-assembly of InAs islands acting as stressors for strain-induced InGaAs(P) quantum dots (SIQDs). The quantum dots are fabricated by growing InAs islands on top of a near-surface InGaAs(P)/InP quantum well (QW). The compressively strained QW affects the size and density of the InAs islands, as compared to islands grown on a plain InP buffer. By adjusting the growth conditions, the height of the InAs stressors is tuned from 15 to 30 nm while the areal density varies around 10 9 cm −2. The confinement of carriers in the SIQDs is characterized by low-temperature photoluminescence. Increasing the size of the InAs stressor is shown to enhance the depth of the lateral confinement potential and reduce the level splitting of excited QD states. However, the small inhomogeneous broadening of the SIQD transitions, as narrow as 11 meV, shows no correlation with the height dispersion of the stressor islands.

Effect of surface states on carrier dynamics in InGaAsP/InP stressor quantum dots

“…Recently, a highly tunable InGaAsP/InP SIQD structure utilizing InAs islands has also been reported [11,12]. The lattice mismatch of the InAs/InP stressors (3.2%) is roughly the same as in the case of the InP/GaAs stressor system.…”

“…The lattice mismatch of the InAs/InP stressors (3.2%) is roughly the same as in the case of the InP/GaAs stressor system. Interestingly, despite the fact that InAs is also a low band gap material (0.42 eV), the SIQDs using InAs stressors have shown good optical characteristics [11,12], contrary to the GaSb stressor system [10].…”

Strain distributions in nano-onions with uniform and non-uniform compositions

“…Although the strain distributions of nano-structured materials (e.g. quantum dot structures) have been studied extensively using continuum approaches and atomistic simulations [38][39][40][41][42][43][44][45][46], no attempt has been made to calculate the strain distributions in nanoonions with non-uniform compositions, taking into account also the surface stress effect. Generally, the quantum dot and matrix are assumed to be isotropic in continuum approaches, and this assumption has been proved to be very reasonable when isotropic and anisotropic solutions for semiconductor materials were compared, and is thus widely used [38].…”

Highly Tunable Emission from Strain-Induced InGaAsP/InP Quantum Dots

“…The details of the sample preparation by metal organic vapor phase epitaxy (MOVPE) are described elsewhere. 6,7) According to atomic force microscope (AFM) images, typical islands density, base diameter and height were 1 Â 10 9 cm À2 , 100 nm, and 23 nm, respectively. The optical properties of the SIQDs were studied by low-temperature (10 K) PL utilizing a frequency-doubled Nd:YVO 4 laser at 532 nm for excitation.…”

“…4(b) as a function of lateral distance from the island center. Neglecting excitonic effects, these calculations were further utilized to determine the energy levels of the SIQDs, 2,6) shown schematically in the inset of Fig. 4(b).…”