Heavy Cr doping of ZnSe by molecular beam epitaxy

Epitaxial ZnSe layers were grown by molecular beam epitaxy (MBE) to study Cr incorporation with the long-term goal of demonstrating an alternate route for achieving transition-metal-doped lasers. Concentrations between 10¹⁵ atoms cm⁻³ and 4×10²⁰ atoms cm⁻³ were achieved. Secondary ion-mass spectroscopy (SIMS) concentration profiles strongly suggest that surface segregation and accumulation of Cr occurs during growth. Photoluminescence (PL) measurements indicate Cr is incorporated in the optically active Cr²⁺ state up to levels of ∼10¹⁹ cm⁻³. Electron paramagnetic resonance (EPR) studies suggest that the Cr atoms exhibit collective magnetic behavior even at these levels. X-ray diffraction (XRD) and reflection high-energy electron diffraction (RHEED) indicate high structural quality is maintained for Cr incorporation for levels up to ∼10¹⁹ atoms cm⁻³.