OPTICAL-PROPERTIES OF PBSE PB1-XMNXSE MULTIPLE-QUANTUM-WELL STRUCTURES/

The electronic structure and optical properties of narrow-gap PbSe/Pb1 -xMn(x)Se quantum-well structures are investigated experimentally and theoretically. The samples were grown by molecular-beam epitaxy along the (111) growth direction and were characterized by high-resolution x -ray diffraction, using triple-axis diffractometry. Their optical prop erties were investigated by transmission and photoconductivity experim ents in the midinfrared range using Fourier-transform spectroscopy. Th e experimental data show that PbSe/Pb1-(x)Mn(x)Se has a staggered band lineup which is in agreement with recent data on coherent anti-Stokes Raman-scattering experiments (Geist et al.), from which it was conclu ded that holes are confined in the PbSe and electrons in the Pb1-xMn(x )Se layers. The experimental absorption data are compared with calcula ted data based on a k.p envelope-function approach for the type-II sup erlattice band structure which yields the energy eigenstates, eigenfun ctions, and oscillator strengths. The absorption constant is obtained from an integration over k space, and the refractive index from a Kram ers-Kronig transformation. The calculated fundamental absorption coeff icients are in good agreement with the experimental data. Agreement be tween experimental and theoretical results is best for a normalized co nduction-band-offset range DELTAE(c)/DELTAE(g) = -0.4 to -0.6 (+/-0.2) .