Tunnel injection (TI) structure is a novel construction approach to build quantum dot based lasers keeping their main advantages like low threshold current, high temperature stability, wide spectral range, but overcoming simultaneously typically occurring limitations, like low carrier collection efficiency or low modulation rates due to hot carrier problems.

We present the results of optical spectroscopy measurements (photoluminescence (PL) and photoreflectance (PR)) for investigating the properties of a tunnel injection structure based on InAs/GaAs quantum dots (QDs) and InGaAs/GaAs quantum well (QW) separated by a 3 nm thick GaAs tunneling barrier. A set of samples including QD and QW references has been studied.

First, we take advantage of modulation technique (eg. high sensitivities and absorption character of PR spectra) to probe the electronic structure details (transitions energies, energy levels and band gap discontinuities). Further, we investigate the photoluminescence properties versus temperature to probe the thermal sensitivity of the emission intensity and tuning of the TI device properties. As it shows a very strong influence of the thermal quenching on the PL efficiency. The hydrostatic pressure has been used (up to 15 kbar) to modify the band structure (spectral fine tuning of the device). As expected, it has shown a detuning of the QW and QD ground state energies (the pressure coefficients of both parts the TI structure agree with those for the reference samples). The latter, in general, should cause a decrease in the tunneling probability, however, a very strong increase in the QD PL intensity has been observed with the increase of pressure. Its explanation has been based on a compromise between the phonon assisted tunneling process (pressure induced energy shift with respect to the LO phonon energy) and changes in the probability for carrier escape from the dots out of the active region through the well states.

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