We have measured the avoided crossings between the Cs (n + 4)s smes and the lowest three members of the adjacent n Stark manifold for 20 < n < 24 using a novel technique based on the differences in the pulsed field ionization of the states under study. The measured positions of the avoided crossings are in excellent agreement with values calculated by matrix diagonalization, and the experimentally determined widths of the avoided crossings, which range from 29 to 78 MHz. are in reasonable agreement with the calculated values.
Conduction- and valence-band offsets have been estimated as a function of well layer thickness in Cd
x
Zn1-x
S/ZnS strained-layer superlattices with various compositions using the model-solid theory. Relatively large values of approximately 180-260 meV in the conduction-band offset can be obtained for x=0.2-0.3. The valence-band offset depends strongly on the well layer thickness, while the conduction-band offset is nearly independent of the well layer thickness up to 200 Å. This strained-layer structure was applied to fabricate ultraviolet (UV) laser diodes with multiple quantum wells. Stimulated emission can be observed either under optical pumping at RT or under pulsed injection at 30 K in the spectral range of 357-390 nm. A spectral narrowing in the emission spectrum with increasing current in the UV injection diode was clearly observed in the vicinity of 375 nm at 30 K.
Annealing effects on CdTe crystals and CdTe/GaAs films in Hg have been investigated through the spectral changes of PL (photoluminescence) at 4.2 K. Before annealing, the PL spectrum of CdTe crystals or films is dominated by the excitonic-emission lines, the edge-emission band and two broad bands. After annealing, a marked decrease in intensity of the broad and edge-emission bands in the bulk crystals is observed, while an increase in intensity of the broad bands in the MOCVD-grown CdTe is significant. We will point out from the PL investigations that the Hg annealing plays an important role in the improvement of both the surface and bulk properties.
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