Far-infrared Studies of Compound Semiconductors

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This proposal describes a program of far-infrared (FIR) magnetospectroscopic studies of compound semiconductors, with strong emphasis on layered structures of II-VI compounds and their ternary alloys, including diluted magnetic semiconductors (DMS). There will be four areas of investigations. First, they will employ FIR magnetooptical techniques to study impurity levels of doped epilayers of wide gap II-VI semiconductor compounds and their ternary alloys prepared by molecular beam epitaxy (MBE) and by atomic layer epitaxy (ALE). The focus will be on hydrogenic donor levels, whose characteristic energies (1s - 2p transition, ionization energy, spin splitting in DMS alloys, etc.) correspond to the FIR energy range. Second, they propose to apply these same techniques to the study of impurities in doped II-VI based superlattices and quantum wells, where the impurity levels depend on the quantum well geometry and on impurity distribution. Third, they will use FIR magnetospectroscopy to study quantum wells, superlattices, and interfaces involving narrow gap semiconductors. Fourth, they will investigate antiferromagnetic resonance in manganese based diluted magnetic semiconductors, where such studies can provide definitive information on dynamical spin processes. One of the strengths of the proposed program is that many of the layered structures to be investigated - as well as bulk samples - can be prepared in their own materials preparation laboratory, either by MBE or (in the case of samples for the antiferromagnetic resonance studies) by conventional crystal growth techniques.