Excitonic Dynamics at the Type-II Polytype Interface of InP Platelets

Indirect excitonsare the focus of intense research due to theopportunity of studying degenerate quantum gases and liquids in anexcitonic system. To realize such systems, it is highly advantageousto have as little scattering as possible. A polytype type-II interfaceis formed between wurtzite and zincblende InP due to the band alignment.Electrons gather on the zincblende and holes on the wurtzite sideof the interface. Therefore, electrons and holes that are spatiallyseparated by the interface form indirect excitons with aligned dipoles.This polytype type-II interface is perfectly flat, which limits scattering.Here we report that repulsive interaction between the indirect excitonsis the driving force behind the long-range transport of indirect excitonsalong the interface at high exciton densities. This is indicativeof less scattering than in conventional type-II heterostructures.The spatial separation of the charge carriers across the interfaceleads to a low recombination rate of the indirect excitons since theoverlap of the electron-hole wavefunction at the interfaceis small. Emission from the long-lived indirect excitons can be detectedeven after 40 & mu;s. Our studies have been performed by using spatiallyand temporally resolved photoluminescence at the low temperature.