Phosphorus and Gallium Diffusion in Ge Sublayer of In0.01Ga0.99As/In0.56Ga0.44P/Ge Heterostructures

Abstract

This chapter gives a short review on dopant diffusion in germanium and specifies the underlying mechanisms of diffusion that involve the point defects. Box-shaped diffusion profiles are discussed that may be described as the phosphorus diffusion controlled by doubly ionized vacancies. In this mechanism, the diffusion coefficient depends on the electron concentration. The particulars of P and Ga diffusion profiles in the Ga-doped substrate of In 0.01 Ga 0.99 As/In 0.56 Ga 0.44 P/Ge heterostructures for multilayer solar cells are discussed. To calculate the diffusion coefficient, two methods were used: the Boltzmann-Matano (version of Sauer-Freise) and the coordinate-dependent diffusion analysis. It is established that coordinate-dependent diffusion analysis, which involves drift components together with diffusion components for diffusion profile description, is more suitable for description of the experimental profiles in such structures near p-n junction. A strong influence of intrinsic electric field on the dopant diffusivity was detected.

Broadband PureGaB Ge-on-Si photodiodes responsive in the ultraviolet to near-infrared range

“…In Figure 7a responsivity is also simulated for yj set at 20 nm, 50 nm and 100 nm. The lower responsivity for 406 nm and 670 nm could be explained by a deeper junction depth which could be caused by Ga diffusion into Ge during 700 °C PureB deposition step 43,44 . However, variations in yj were not able to explain the low measured responsivity in the NIR range.…”