Photoreflectance and photoluminescence, supported by the energy level calculations in the eight-band k⋅p model including strain, have been used to study the optical properties of GaSb/AlSb/InAs/InGaSb/AlSb/GaSb type II quantum wells (QWs). The broad emission wavelength tunability in the midinfrared range has been demonstrated by the control of InAs layer thickness. The temperature dependent measurements have shown that the emission can still be efficient at room temperature in such structures, and that the temperature shift of the fundamental type II optical transition between 10 and 300 K can be significantly smaller than for type I QW systems.

We present optical studies of quantum dot tunnel injection structures for 1.3 μm emission with an InGaAsN quantum well injector. Photoreflectance spectroscopy supported by effective mass calculations within the band anticrossing model has been used to identify the optical transitions. Based on that, an evidence of the tunneling from the injector well to the dots could be detected by photoluminescence excitation up to the free carrier regime at room temperature. The latter finds confirmation in shortened photoluminescence rise times, when compared to the injector-free quantum dot reference structure.

Ga N 0.02 As 0.87 Sb 0.11 ∕ Ga As single-quantum wells have been investigated by photoreflectance (PR) at room temperature. PR features related to the ground and excited state transitions have been clearly observed. The experimental data have been compared with the calculations in the envelope function formalism taking account the effect of strain. The band gap lowering and the increase in the electron effective mass due to the incorporation of nitrogen atoms into GaAsSb have been included. Excellent agreement between experimental data and calculation results have been found for band structure Type-I with the conduction-band offset ratio of 50%.

Band structure properties of the type-II W-design AlSb/InAs/GaIn(As)Sb/InAs/AlSb quantum wells have been investigated theoretically in a systematic manner and with respect to their use in the active region of interband cascade laser for a broad range of emission in mid infrared between below 3 to beyond 10 μm. Eight-band k·p approach has been utilized to calculate the electronic subbands. The fundamental optical transition energy and the corresponding oscillator strength have been determined in function of the thickness of InAs and GaIn(As)Sb layers and the composition of the latter. There have been considered active structures on two types of relevant substrates, GaSb and InAs, introducing slightly modified strain conditions. Additionally, the effect of external electric field has been taken into account to simulate the conditions occurring in the operational devices. The results show that introducing arsenic as fourth element into the valence band well of the type-II W-design system, and then altering its composition, can efficiently enhance the transition oscillator strength and allow additionally increasing the emission wavelength, which makes this solution prospective for improved performance and long wavelength interband cascade lasers.