In situ reflectance difference spectroscopy of p-type ZnTe:N grown by MBE

Abstract

In situ Reflectance Difference Spectroscopy (RDS) was performed during p-type of nitrogen-doped ZnTe thin films grown by Molecular Beam Epitaxy (MBE). The MBE system is equipped with an electron cyclotron resonance (ECR) cell for N-plasma generation. The RDS system is attached via a strain-free fused silica viewport mounted for normal incidence. This allows us to take RD spectra during the doping process in the range from 1.5 to 5.5 eV. The doping level of the ZnTe:N films was determined in situ by evaluating the RD spectra in the vicinity of the E 1 and E 1+Δ 1 transitions. This spectral range was used to get the optimum conditions in the online doping performance of the plasma cell. We varied cell parameters like N-pressure and input r.f. power. Furthermore, we investigated doping-induced surface processes, like surface saturation with activated N-species. Finally, ex situ measured spectra are compared with in situ acquired data, in order to study the surface Fermi level pinning at ambient pressures.