Effects of reduced growth temperature on crystalline qualities and dopant diffusion in Pb 1− xSn xSe/PbSe layers grown by MBE

Abstract

The MBE growth of lead tin selenides (Pbi 1− x Sn x Se: LTS)/PbSe double layers was carried out, and the effects of reduced growth temperature on crystalline qualities of upper LTS layers and diffusion of dopants at the interface between LTS and PbSe were investigated. A few micrometer-thick PbSe epitaxial layers (undoped) were directly grown on the CaF 2 (111) substrates at 485 °C and then the Bi or Bi 2Se 3 doped LTS layers were grown on top of PbSe at 200–485 °C. It was found that epitaxial temperature could be reduced to 200 °C. Reflection high energy electron diffraction (RHEED) patterns and full width at half maximum (FWHM) values of X-ray rocking curves in LTS indicated that crystalline qualities of LTS layers tended to degrade at lower temperature than ~ 300 °C. Deviation from the abrupt change in dopant concentrations at the interface was observed by secondary ion mass spectroscopy (SIMS) analysis, suggesting possible diffusion of dopant from LTS into PbSe. In the case of diffusion of Bi from LTS ( n ~ 10 18 cm −3) into undoped PbSe ( p ~ 10 17 cm −3), deviation was as small as 500 Å and the value of diffusion coefficient was roughly estimated as that of the order of 10 −15 cm 2/s at 300–400 °C.