MBE Growth and Optical Properties of Isotopically Purified ZnSe Heterostructures

Wide-gap II/VI heterostructures (HS) and quantum wells (QW) composed of ZnSe, CdSe, MgSe, and their ternary and quaternary compounds are attractive candidates for modern quantum optical devices such as single photon sources and optically controlled spin qubits in the visible spectral range. In contrast to similar III/V semiconductor based devices, generally, most of the II/VI compounds allow for isotope purification toward zero-nuclear-spin species in the semiconductor environment. Using the same molecular beam epitaxy (MBE) system for natural and isotopically purified materials opposes the challenge of achieving superior isotope purity, for example, of Zn and Se species on the background of operation of the other effusion cells filled with natural isotopes. Here we report on the crystallographic and optical properties of ZnMgSe/ZnSe heterostructures and quantum wells grown by using Zn-64 and Se-80 isotopes and Mg with natural isotope distribution. We present a detailed quantitative secondary ion mass spectrometry (SIMS) analysis, which confirms that an extremely high grade of isotope purification of the ZnSe can be maintained, although natural and enriched Zn and Se elements are used in the same MBE system. This pioneering growth study forms a solid base to generate a spin vacuum ZnSe host crystal that is particularly suited for future studies on the dynamics of localized spins in II/VI heterostructures on a strongly extended coherence time scale.