Photoelectric and deep level study of metamorphic InAs/InGaAs quantum dots with GaAs confining barriers for photoluminescence enhancement

摘要

Metamorphic InAs/InGaAs quantum dots (QDs) have been proposed as active elements for optoelectronic light-emitting devices operating in the infrared range. However, advanced structure design to allow efficient and stable enhancement of quantum yield at room temperature are still needed. Here, we compare a metamorphic InAs/In0.15Ga0.85As QD heterostructure with and without GaAs confining barriers, to investigate the effect of introducing GaAs barriers on the photo- and thermo-electrical properties. GaAs confining barriers allow to enhance the QD photoluminescence intensity at 1.3 mu m, i.e. second telecommunication window, by more than two orders of magnitude at room temperature and at 80 K. We also discuss the effect of GaAs barriers on the carrier transport and on defect-related levels detected by means of photocurrent and deep level thermally stimulated current spectroscopies. GaAs confining barriers decrease the thermal escape rate of electrons confined in QD and wetting layer, thereby highly increasing the radiative recombination and also quenching the photocurrent. At low temperatures, the barriers also reduce the capture of electrons generated in InGaAs by the QD layer and, on the other hand, prevent the trapping of electrons outside the QD layer, decreasing carrier lifetimes. The deep levels identified as point and extended defects have been detected in the InGaAs layers. There are no new types of defects introduced in the structure by the addition of the barriers, but this causes a weakly increased density of traps near QDs. Our results show that InAs/InGaAs QDs with GaAs confining barriers can be efficient light emitters with only a slight increase of defects in the structure. Hence, such advanced design for metamorphic QDs can be of relevant interest for applications in energy-efficient QD lasers, optical amplifiers and single-photon emitters operating at 1.3-1.55 mu m.