Te Multiple Quantum Wells Research Articles

Structure of CdTe-Cd1−xMnxTe multiple quantum wells grown on (001) InSb substrates by molecular beam epitaxy

Molecular beam epitaxy has been used to prepare multiple quantum well structures of CdTe/Cd1−xMnxTe on (001) InSb substrates. The growth of such a system on InSb allows the use of particularly low growth temperatures, hence minimizing interdiffusion effects. This study presents the first transmission electron microscope investigation of this multilayer system grown on InSb. The work clearly demonstrates that multiple quantum wells of high structural quality can be grown reproducibly over a wide range of layer thicknesses. The importance of efficient substrate surface cleaning prior to growth is demonstrated. In order to grow high structural quality multilayers, the choice of buffer layer is also important and a possible explanation for this observation is given.

Radiative recombination in PbTe quantum wells

Recombination of quasi-two-dimensional (2D) free-electron-hole pairs in PbTe/(Pb,Eu)Te multiple quantum wells has been studied in time-resolved photoluminescence experiments in the 4–5 μm region on subnanosecond scale by an infrared upconversion method. Over a finite temperature range, the recombination rate is seen to vary approximately as 1/T, as expected for a radiative process in a nondegenerate 2D carrier gas. A model is presented where the recombination is enhanced by the presence of a substantial background hole density in the PbTe wells, generated in a manner analogous to modulation doping.

Resonant Raman scattering and exciton-optical phonon coupling in CdTe/(Cd,Mn)Te quantum wells

Resonant Raman scattering at the E0 gap from longitudinal optical phonons in CdTe/(Cd,Mn)Te multiple quantum wells has been studied near the strain split n=1 exciton ground state. A large resonance enhancement is observed with distinct incoming and outgoing channels, in agreement with luminescence excitation spectra. Phonons are observed from CdTe wells and (Cd,Mn)Te barriers, indicative of small valence-band offsets for this superlattice system. At extreme resonance, striking linewidth broadening and damping effects for the alloy phonon modes are witnessed.

Time-resolved exciton recombination in CdTe/Cd1−xMnxTe multiple quantum wells

The lifetime of excitons in CdTe/Cd1−xMnxTe multiple quantum wells at low temperature has been measured by time-resolved photoluminescence in samples of different well thickness. The excitons, which have elsewhere been shown to be localized preferentially near the heterointerfaces, possess an average lifetime which becomes shorter with decreasing well thickness and increasing external magnetic field. The results are in qualitative agreement with the expectations for a localized quasi-two-dimensional exciton with a large radiative recombination cross section.

Interface localization of excitons in CdTe/Cd1-xMnxTe multiple quantum wells.

Photoluminescence in undoped CdTe/${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Mn}}_{\mathrm{x}}$Te multiple quantum wells at low temperatures shows highly efficient excitonic emission. By studying the emission spectra as a function of temperature, external magnetic field, and its dependence on well thickness, we have obtained strong evidence for the importance of the heterointerface in providing centers of localization for excitons in these strained-layer structures.