N -type doping of lattice-matched ZnCdSe and ZnxCdyMg1−x−ySe epilayers on InP using ZnCl2

Chlorine on Se-site forms a shallow donor for ZnSe. In this article, we use Cl, obtained from ZnCl2, as the n-type dopant for ZnxCdyMg1−x−ySe lattice matched to InP, a new wide band gap II-VI material grown by molecular beam epitaxy. An 800 Å p-type doped InGaAs buffer layer was grown to improve the doping behavior, consistent with improved crystalline quality. The highest free-carrier concentrations measured by Hall effect are 7×1018 cm−3 with mobility of 240 cm2/V s and 3×1018 cm−3 with mobility of 230 cm2/V s for Zn0.5Cd0.5Se (77 K Eg=2.17 eV) and ZnCdMgSe (77 K Eg=2.74 eV), respectively. A small systematic reduction of maximum carrier concentration was observed as the quaternary layer band gap is increased. No deep level emission is introduced by the chlorine dopant. High n-type doping levels, consistent with semiconductor laser applications were achieved for quaternaries of band gaps as high as 2.9 eV.