The conventional approach to fabricate semiconductor based QDs is based on the Stranski-Krastnow (SK) growth mode,
which has enjoyed considerable success in device applications. However, the SK QD approach is complicated by the
randomness of the QD size distribution and inherent presence of the wetting layer. Carrier leakage to the wetting layer
has been identified as one of the underlying causes for low optical gain and high temperature sensitivity in diode lasers.
To fully exploit the potential advantages of ideal Quantum Dots (i.e. full 3D carrier confinement), elimination of the
wetting layer and a uniform mono-modal QD size distribution is needed. Nanopatterning with selective MOCVD QD
growth has potential for achieving a higher degree of control over the QD formation, compared with the SK process.
Furthermore, the problematic wetting layer states are eliminated and improved optical gain is expected. The QD
patterning is prepared by dense nanoscale (20-30 nm diameter) diblock copolymer lithography, which consists of
perpendicularly ordered cylindrical domains of polystyrene-block-poly(methylmethacrylate) (PS-b-PMMA) matrix. For
selective MOCVD growth, a dielectric template mask was utilized and the polymer patterning is transferred on it. The
resulting GaAs QD densities are larger than 5×1010/cm2, comparable to SK growth mode, with a nearly monomodal QD
size distribution. Variable temperature PL has been used to characterize the optical properties of capped InGaAs QDs on
GaAs (λ ~ 1.1 μm) and InP (λ ~ 1.5 μm) substrates.