Photoluminescence study of InAs/InGaAs sub-monolayer quantum dot infrared photodetectors with various numbers of multiple stack layers

This study investigated the effects of the number of stacking layers (S) on the optical properties of InAs/InGaAs sub-monolayer quantum dot (SML-QD) infrared photodetectors by photoluminescence spectroscopy. As S was increased from two to six, the room temperature PL emission energies were redshifted remarkably (~84 meV) and the full width at half maximum was increased by approximately 10 meV due to a change in the size distribution of SML-QDs. Furthermore, the excitation intensity-dependent PL spectra of the SML-QD (S = 6) showed improved PL integrated intensity caused by a change in the QD distribution and density. With increasing S, the carrier thermal activation energies (E_a) for the InAs QD and InGaAs quantum well (QW) increased by approximately 27 and 8 meV, respectively, due to the QD size effect. These results suggest that the mini-band structure of multiple SML-QDs formed with a very thin spacer thickness (~1 nm) could be tuned by controlling S.