Characteristics of Cl-doped ZnSe layers grown by molecular-beam epitaxy

Abstract

High‐quality n‐type ZnSe layers have been grown by molecular‐beam epitaxy using chlorine (Cl) as a dopant. The Cl‐doped ZnSe layers showed mirrorlike morphology and good crystallinity, although some degrade in crystallinity is observed at a heavy doping. The carrier concentration of the layer could be widely controlled by a ZnCl₂ Knudsen cell temperature. The carrier concentration attained 1×10¹⁹ cm⁻³, where the resistivity was as low as 3×10⁻³ Ω cm, indicating a remarkable improvement compared to the previous work using group‐III elements as a dopant. Hall mobilities at room temperature were in the range of 200–400 cm²/(V s), depending on the doping level. The Cl‐doped ZnSe layer exhibited strong blue near‐band‐gap photoluminescence (PL) with suppressed deep‐level emission at room temperature. The 4.2‐K PL of the layer was dominated by strong emission of excitons bound to neutral donors originating from substitutional Cl atoms. It was found by a secondary ion‐mass‐spectroscopy analysis that diffusion of Cl atoms in the ZnSe layer during growth was negligible (<370 Å).