Investigation of the quantum confinement anisotropy in a submonolayer quantum dot infrared photodetector

A submonolayer quantum dot infrared photodetector (SML-QDIP) was grown on a GaAs(001) substrate by molecular beam epitaxy and processed using conventional optical lithography, wet etching and electronbeam metallization. Additionally, a side of the device was polished at 45 degrees in order to allow optical measurements with s- and p-polarized light. The electro-optical properties of the device were investigated both in normal incidence and at 45 degrees in order to study the quantum confinement of the SMLQD along the lateral and vertical directions. The s-to-p photocurrent ratio was found to be between 0.10 and 0.43, showing that, in this new type of quantum dot, the lateral confinement is still weaker than along the vertical direction, but is better than the one of conventional QDs fabricated in the Stranski-Krastanov growth mode. The maximum specific detectivity in normal incidence was $1.3 \times 10^{11}$ cm Hz1/2/W at 30 K and 0.9V.