Formation and Optical Characteristics of Type-II Strain-Relieved GaSb/GaAs Quantum Dots by Using an Interfacial Misfit Growth Mode

We report the formation and optical characteristics of GaSb/GaAs type-II quantum dots (QDs) by using an interfacial misfit (IMF) growth mode. A V/III ratio during the growth of GaSb QDs determines the selectivity of IMF and conventional Stranski–Krastanov (SK) growth modes. This transition between SK and optimized IMF QDs is rather abrupt and occurs within a factor-of-2 variations in V/III ratio. The IMF QDs emit at longer wavelength ($cong {1.1} mu$m) compared to the SK QD peak emission at $ cong {1.02} mu$m at low temperature (LT) (4 K) because of their strain-free nature of the IMF growth mode. A blueshift of the photoluminescence (PL) peak is observed with increased excitation densities due to the Coulomb interaction between physically separated electrons and holes characteristics of the type-II band alignment. LT time-resolved PL measurements show a long decay time of $ cong {20}$–40 ns from the transition between GaSb IMF QDs and GaAs 2-D electron gas, which is characteristic of the type-II band alignment.