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

Band structure calculations are performed by k . p theory on lattice-matche d (LM) and strain-compensated (SC) interdiffused GaInAs(P)/GaInAsP quantum wells (QWs) designed for 1.55 mu m wavelength response. The evolution of th e in-plane band structures as a function of the diffusion length (up to 5 n m) 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 be haviors in the curves of density of states. These arise from electron-like subbands and are strongly modified after interdiffusion. The in-plane effec tive masses of carriers involved in the fundamental excitonic transitions i ncrease by 15% (electrons) and 25% (holes). The subband tightening trend is strongly marked in the case of SC structures with uniform cationic composi tion, for which narrow QWs are required. On the other hand, this trend is w eak 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 conf ined. Since inplane motion of confined holes involves HH and light hole (LH ) mixing, this restricts the dynamic characteristics expected for these str uctures. (C) 2000 Elsevier Science B.V. All rights reserved.