Quantum dot formation with silicon doping in InGaN/GaN quantum well structures and its implications in radiative mechanisms

Optical properties and material microstructures of three InGaN/GaN quantum well (QW) samples with various silicon-doping concentrations in barriers were measured. From the high-resolution transmission electron microscopy images, quantum dots (QDs) of a few nm in size were observed in silicon-doped samples. The regularities of QDs in size, shape and distribution increased with doping concentration up to 5 × 10¹⁸ cm^-3. Such observations implied that the reduction of quantum-confined Stark effect in such a sample was due to the relaxation of strain energy in QDs with silicon doping, besides the carrier screen effect. In other words, the microstructures were crucially changed with silicon doping in barriers. Also, the carrier localization effect was actually enhanced although potential fluctuation indeed became less randomly distributed. The calibrated radiative lifetimes in both silicon-doped samples showed the consistent trend of the formation of 0-D structure upon silicon doping.