MOVPE prepared InAs/GaAs quantum dots covered by GaAsSb layer with long wavelength emission at 1.8 µm

Abstract

Preparation and properties of InAs/GaAs quantum dots (QDs) prepared by the MOVPE technology covered by GaAsSb strain reducing layer (SRL) with extremely long emission wavelength at 1.8µm will be presented. Increase of the emission wavelength was achieved by the introduction of GaAsSb SRL with Sb content of about 30% in the solid phase. The high Sb concentration in the SRL causes the preservation of QD size, which is about 15nm wide at the base and 5nm high. Increased QD size increases the photoluminescence (PL) wavelength. Furthermore, high content of antimony leads to a creation of type II heterostructure for which a redshift of the PL wavelength and decrease of the PL intensity are typical. Low PL intensity may complicate light emitting applications; however fast separation of carriers in the type II structure is an advantage for detector or solar cell application, especially with the long working wavelength. With respect to the perspective application of this structure, the photocurrent (PC) measurement was chosen as the complementary characterization method. A depression of PC for quantum well wavelength region (approximately 900–1200nm) was observed for positive bias, while the PC from QDs (over 1200nm) is not sensitive to the electric field orientation at all. An explanation of this unexpected phenomenon is suggested.