Femtosecond measurement of electron capture and intersubband relaxation in self-organized InAs quantum wires on In_{1 − x}Al_xAs/InP

We have investigated the electron dynamics in high-density InAs self-organized quantum wires on In_{1 − x} AlM_x As/InP (001) using pump-probe transmission with a midinfrared probe tuned to an intersubband transition in the conduction band. At low carrier densities, we have measured an effective capture time from the barrier to the first electron subband of 3 ps, longer than in quantum wells, and an intersubband scattering time from the second to the first subband of 0.4 ± 0.1 ps. We attribute both processes to the interaction with LO phonons. For carrier densities above 3 × 10⁵cm⁻¹, Auger processes lead to larger capture rates.