Electronic structure of interdiffused GaInAs(P)/GaInAsP quantum wells

Band structure calculations are performed by k·p theory on lattice-matched (LM) and strain-compensated (SC) interdiffused GaInAs(P)/GaInAsP quantum wells (QWs) designed for 1.55 μm wavelength response. The evolution of the in-plane band structures as a function of the diffusion length (up to 5 nm) is presented and discussed. The subbands are tightened with consecutive changes in their curvatures and interactions. In the case of LM structures, a densely packed valence subband structure is found with spiky singular behaviors in the curves of density of states. These arise from electron-like subbands and are strongly modified after interdiffusion. The in-plane effective masses of carriers involved in the fundamental excitonic transitions increase by 15% (electrons) and 25% (holes). The subband tightening trend is strongly marked in the case of SC structures with uniform cationic composition, for which narrow QWs are required. On the other hand, this trend is weak in the case of SC structures with uniform anionic composition, in which QWs are rather wide. In this latter case, a good stability in the optical properties of the structures after thermal processing is expected. However, due to the tensile strain in the wells, only heavy holes (HHs) can be confined. Since in-plane motion of confined holes involves HH and light hole (LH) mixing, this restricts the dynamic characteristics expected for these structures.