Influence of thiol coupling on photoluminescence of near surface InAs quantum dots

Photoluminescence (PL) of near surface InAs quantum dots (QDs) has been studied as a function of the distance to the surface (30, 20, 10, 6 nm). We observe a strong decrease in the QD PL intensity with decreasing barrier thickness. Nevertheless, the QDs still show reasonably strong PL intensity even when they are only 10 nm beneath the surface. After the deposition of self-assembled monolayers of octadecylthiol, we observe an increase in PL intensity up to a factor of 1.87. Such an enhancement is attributed to a decrease in the density of surface states. This demonstrates that near surface InAs QDs are very sensitive to changes of the surface conditions and the deposition of octadecylthiol monolayer may be used to increase their sensitivity, which is promising toward future bio-sensor applications.