Studies of Photoreflectance in Cd 1-x Mn x Te/Cd 1-y Mn y Te Superlattices
- PDF / 300,341 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 41 Downloads / 207 Views
ABSTRACT Photoreflectance spectroscopy has been peformed on a series of Cdl.×MnxTe/Cd,.yMnyTe superlattices. Samples were grown on (001) GaAs substrates by molecular-beam epitaxy with different barriers (x=0.3 to 0.8) and wells (y=0 to 0.01). After taking into consideration the strain-induced and quantum confinement effects, the exciton transition energies of the heavy and light holes can be determined using envelope-function calculations. The calculations are in good agreement with the photoreflectance measurement results. These results show that photoreflectance is a powerful probe for the study of quantized state structures in superlattices. INTRODUCTION Diluted magnetic semiconductors (DMS) are compounds in which a fraction of the nonmagnetic cations is randomly substituted by magnetic ions. The most extensively studied materials of this type are the Mn based I1-VI alloys Al.xlIMnxBvl, for example Cd,.-MnxTe. The strong exchange interactions (sp-d exchange), and the interaction between localized magnetic ions (d-d exchange) in these materials lead to a series of interesting magnetic-optical properties, such as extremely large Zeeman splitting, the giant Faraday effect, the formation of bound magnetic polarons, the magnetic induced type I to type II superlattice (SL) transition, and spinflip Raman scattering."' 2 The recent development of molecular beam epitaxy (MBE) for 11-VI materials allows precisely controlled growth of high-quality DMS, which open new possibility for the study of optical electron devices with DMS. Strain-induced effects play an important role in SLs. The lattice mismatch between the
wells and barriers in a SL lead to an effective hydrostatic tensile (compressive) strain in the layer plane and an uniaxial compressive (tensile) strain along the growth axis. Large strains in the structure strongly modify the conduction and valence band extreme and split the degeneracy of the heavy and light hole valence band edge. There have been relatively few investigations using photoreflectance (PR) spectroscopy on Cd1 ,Mn,,Te/Cdl.yMnyTe SLs and those reported only deal with a small composition range (x
Data Loading...
