SUPPRESSION OF OUT-DIFFUSION EFFECT OF DOPANTS BY THE HfO2 DIFFUSION BARRIER FOR HIGHLY N-DOPED GE EPILAYERS GROWN ON SI(001) SUBSTRATE

Abstract

Ge is a potential candidate for the realization of Si-based light sources that are compatible with CMOS technology. Electron doping in Ge is an efficient method to modify its band gap structure to enhance the radiative recombination of Ge film. Post growth thermal treatment is a necessary step to activate the dopants and ameliorate the film’s crystal quality. Thermal annealing process at high temperature resulting the out-diffusion effect of dopant, such as Sb or P element. In this paper, we present the role of diffusion barrier using HfO₂ layer on the prevention of the dopant segregation on the surface. The Ge film is grown on Si substrate by molecular beam epitaxy (MBE) technique. It is worth noting that in the case of n-doped Ge epilayers with the HfO₂ barrier, the PL intensity increases by a factor of 1.6 compared to that of the free barrier sample. However, tensile strain in Ge film is not affected by the HfO₂ layer and remains the value of about 0.20% after annealing at 750^oC in 60 secs.