Realization of the Esaki-Tsu-type doping superlattice

Abstract

A type-A (Esaki-Tsu type) doping superlattice has been obtained by using the δ-doping technique and employing very small superlattice periods, on the order of the electron de Broglie wavelength. Such superlattices exhibit quantum-mechanical coupling of electron and hole wave functions in adjacent quantum wells resulting in finite z dispersion. Clear experimental evidence of having realized an Esaki-Tsu type of doping superlattice is supported by optical emission and absorption properties, from photoluminescence and photoconductivity measurements, as well as perpendicular transport properties. The measurements reveal (i) stable emission and (ii) absorption of radiation below the bulk band gap of GaAs. Efficient transport in the superlattice growth direction is found for doping superlattices with small periods. These results are interpreted as direct evidence for the realization of a type-A doping superlattice, whose properties deviate significantly from the type-B doping superlattice with long periods.