Encapsulation study of MOVPE grown InAs QDs by InP towards 1550 nm emission

Abstract

The three-dimensional carrier confinement in Quantum Dots (QDs) is the key to achieve superior properties (electronic and optical) compared to the Quantum Well (QWL) for optoelectronic applications, such as semiconductor lasers, photodiodes. After the growth of QDs, the encapsulation is the next crucial step to confine carriers in QDs and achieve the targeted wavelength emission. In this work, we have studied the InP capping of Stranski-Krastanov (S-K) grown InAs QDs on InP(0 0 1) substrate by MOVPE. During the encapsulation, the P/As exchange is a vital process which either transforms the QDs into a 2D layer or reduces QDs' dimensions. This study shows that a control of Phosphorous concentration on the surface during InP capping facilitates to obtain the expected QDs dimension for 1550 nm wavelength. The emitted photoluminescence peak shifts following the preserved average QDs' dimensions. By combining simulation with optical response we have proved the Phosphorous incorporation into the InAs structure (QDs or 2D layer) during the encapsulation step. As expected, the carrier lifetime reveals the superior quality of the preserved QDs in InP barrier compared to the 2D layer. Finally, the reduction of the non-radiative recombination sources, e.g. dangling bonds, by passivation treatment demonstrates a further increment in carrier lifetime.