MOLECULAR BEAM EPITAXY OF WIDE GAP II-VI SUPERLATTICES (ZINC-SELENIDE, CADMIUM-TELLURIDE, MANGANESE)
Abstract
Considerable attention is now focussed on the II-VI class of semiconductor compounds. This renewed interest is motivated by the many degrees of freedom offered in the growth of these II-VI compounds by molecular beam epitaxy. A variety of II-VI semiconductors such as CdTe, (Cd,Mn)Te, ZnSe, and (Zn,Mn)Se have been grown by MBE and each material system has exhibited unique properties with potential for device applications. For the case of the MBE growth of CdTe on (100) GaAs (14.6% lattice constant mismatch), two epitaxial orientations occur; either (111) CdTe or (100) CdTe can be selectively grown on (100) GaAs. High resolution electron microscopy, used to investigate the nature of the two interfaces, has aided in solving the puzzle as to which factors determine a specific orientation. Such a unique situation, involving the existence of two orientations, has enhanced identification of the role of the superlattice heterointerface on the excitonic behavior of the (Cd,Mn)Te superlattice system. The ZnSe and (Zn, Mn)Se material systems also possess interesting features. To use ZnSe as the well material and (Zn,Mn)Se as the barrier material in a superlattice configuration, metastable, zincblende Zn(,1-x)Mn(,x)Se was necessary with high Mn mole fraction (0.20 < x (LESSTHEQ) 0.66) to provide carrier confinement. The superlattice structures have exhibited lasing and nonlinear excitonic saturation. In addition to Mn acting to modulate the bandgap, its presence introduces magnetic properties which is a unique feature for semiconductor superlattices. Superlattice structures consisting of ZnSe wells ((LESSTHEQ)50(ANGSTROM)) perturbed by the insertion of ultrathin layers of MnSe (3(ANGSTROM) to 12(ANGSTROM)) have been grown. Although MnSe is antiferromagnetic, optical measurements indicate that these two-dimensional magnetic "sheets" exhibit paramagnetic behavior.
Degree
Ph.D.
Subject Area
Electrical engineering
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