Strain compensated CdSe/ZnSe/ZnCdMgSe quantum wells as building blocks for near to mid-IR intersubband devices

In order to increase the conduction band offset of the ZnCdMgSe-based material system we studied the incorporation of strained Cd/Se layers to obtain deeper quantum wells for shorter wavelength intersubband transitions than those obtained in lattice matched structures. Five CdSe/ZnSe/ZnCdMgSe multi quantum wells (QW) samples grown by molecular beam epitaxy are studied in detail by transmission electron microscopy (TEM), X-ray diffraction (XRD), cw-photoluminescence (PL), and Fourier Transform Infrared (FTIR) absorption experiments. TEM and XRD results confirmed good structural quality of the samples. All the multi-QW PL energies were below the ZnCdSe lattice matched to InP alloy bandgap (2.1 eV), which serves as first evidence of having achieved deeper quantum wells. FM absorptions from 3.83 to 2.56 mu m were measured, shorter than those achieved by the lattice matched system. Simulations based on these results predict that absorptions as low as 2.18 mu m can be obtained with these materials. (C) 2015 Elsevier B.V. All rights reserved.