Transport of Dipolar\nExcitons at the Type-II Polytype\nInterface of InP Platelets

The pursuit of high charge carrier mobility in nanostructures\nis\ncrucial for advancing both device development and exploring fundamental\nphysics. This study focuses on minimizing scattering to achieve high\nmobility, employing a polytype type-II interface formed between wurtzite\nand zincblende InP. On the zincblende side, electrons accumulate,\nwhile holes gather on the wurtzite side, resulting in the creation\nof spatially separated indirect excitons with aligned dipoles. The\nperfectly flat polytype type-II interface serves to minimize scattering.\nFurthermore, modulation doping is implemented to reduce Coulomb scattering,\nachieved by doping the entire wurtzite segment n-type, excluding the\nvicinity of the interface. The investigation particularly focuses\non understanding the impact of doping on the spatial distribution\nof indirect excitons at polytype type-II heterointerfaces. Spatially\nand temporally resolved photoluminescence spectroscopy at low temperatures\nis utilized to explore the spatial distribution and recombination\ndynamics of indirect excitons. The study reveals a significantly reduced\nspatial distribution and enhanced recombination rate of indirect excitons\nin the presence of an electron background for the n-type doped platelets\ncompared to the undoped platelets. This aligns with expectations due\nto enhanced recombination rates provided by numerous electrons. Additionally,\nwe were able to estimate a lower limit for the expansion speed of\nthe indirect excitons at high excitation power density in undoped\nplatelets.