Enhanced photoconductive signal in InAs quantum dots due to plasma confined microcavities

Wave functions and oscillator strengths for interlevel transitions in InAs dots embedded in an InAlAs matrix, calculated using an eight-band strain-dependent k⋅p Hamiltonian are compared to measured photoconductive spectra. Several polarized peaks are present in the 80–400-meV range. A large peak is present around 160 meV for side illumination, in spite of small oscillator strength, while it is absent for normal incidence, and as a result of absorption. The high carrier concentrations of the contact layers produce a unique cavity. As the plasma frequency is approached, the real part of the refractive index drops. Radiation entering from the side is totally internally reflected, while front illumination is completely reflected. This effect of the plasma-confined microcavity was not reported previously, to the best of our knowledge.