In situ reflectance difference spectroscopy of II-VI compounds: A real time study of N plasma doping during molecular beam epitaxy

Reflectance difference spectroscopy (RDS) has been performed during the gro wth and nitrogen-doping process of II-VI layers fabricated by molecular bea m epitaxy (MBE). To the MBE chamber, equipped with an electron cyclotron re sonance cell for N plasma generation, a RDS system has been attached via a normal incidence viewport which allows the acquisition of spectra during th e doping process in the spectral range from 1.5 to 5.5 eV. ZnTe (001) surfa ces have been studied under varying exposure conditions, like Zn, Te, and/o r N plasma flux onto the sample surface. Furthermore, RDS features in the v icinity of the E-1 and E-1 + Delta(1) transitions were used to optimize onl ine the doping performance of the N plasma cell by varying the source param eters, like N pressure and input power. Doping induced surface processes an d surface saturation with activated N species have been investigated. Ex si tu measured spectra are compared with it? situ acquired data to study the s urface Fermi level pinning occurring at ambient pressures. Finally, in situ acquired RDS data of delta-doped ZnSe are presented. (C) 1999 American Vac uum Society. [S0734-211X(99)07404-1].