Impact of Excited States Transitions on Polarization Property of InAs/InP Quantum Dots

Abstract

Self-assembled InAs/InGaAsP/InP quantum dots (QD) have been investigated intensively, in which polarization property is a key performance indicator in some photonic devices, such as semiconductor QD optical amplifiers. Conventionally, increased transverse magnetic (TM) polarization is achieved by increased heavy-hole (HH) - light-hole (LH) mixing, such as using closely stacked QDs with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">large</i> stacking layer number (SLN), which was predicted by previous theoretical works and verified experimentally. However, high TM polarization in the closely stacked QDs with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">small</i> SLNs was not predicted by the current theory but confirmed experimentally. In this work, closely stacked InAs/InGaAsP/InP QDs with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">small</i> SLNs are investigated including strain, piezoelectricity and spin-orbit interaction. It is found that the high TM polarization in the closely stacked InAs/InP QDs with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">small</i> SLNs is attributed to strong first excited state transitions and thus more p-type wavefunctions involved, rather than the high HH-LH mixing. With increase of SLN, TM polarization contributed by first excited state transitions decreases, while it contributed by the HH-LH mixing increases.