Interband and Intersubband Optical Properties of Doped n- $hbox{Zn}_{bf 0.46}hbox{Cd}_{bf 0.54}hbox{Se/Zn}_{bf 0.24}hbox{Cd}_{bf 0.25}hbox{Mg}_{bf 0.51}hbox{Se}$ Multiple Quantum Wells for Intersubband Device Applications

Two heavily doped n-type Zn_0.46Cd_0.54Se/Zn_0.24 Cd_0.25Mg_0.51Se multiple quantum well (MQW) structures have been grown on InP (0 0 1) substrates by molecular beam epitaxy. Photoluminescence (PL), time-resolved PL, and Fourier transform infrared (FTIR) spectroscopy were performed to characterize their interband and intersubband (ISB) properties. These two MQW samples have similar structures except for different well widths and a different number of periods. Excitation-intensity-dependent PL shows no electronic coupling between the multiquantum wells. The integrated PL intensities and the PL decay times of the MQWs were measured as functions of temperature in the range from 77 to 290 K. Theoretical fittings of temperature dependences of integrated PL intensities and PL decay times indicate that the nonradiative recombination processes observed in our samples can be well described by hole capture by acceptor-like defect centers through multiphonon emissions. ISB absorption spectra of the samples were measured by FTIR and show peak absorption at wavelengths of 3.99 and 5.35 mum for the MQWs with well widths of 28 and 42 A, respectively. Theoretical calculations based on the envelope function approximation confirm that these peaks are due to the transitions from the ground state E₁ to the first excited state E₂.