Carrier Dynamics and Dynamic Band-Bending in Type-II ZnTe/ZnSe Quantum Dots

Carrier dynamics and dynamic band-bending in self-assembled ZnTe/ZnSe quantum dots have been studied by means of time-resolved photoluminescence experiment at low temperatures. The experiment reveals clearly type-II character of the confinement potential in the dot manifested in: (i) long photoluminescence decay time constant of 28-35 ns, and (ii) temporal shift of the quantum dot peak emission towards low energy following the laser pulse excitation. The magnitude of the spectral shift Δ E depends on the dot size and the power density of excitation pulse. For the dots under study and given experimental conditions Δ E ≈ 28 ÷ 42 meV.