Superconducting Layers by Gallium Implantation and Short-Term Annealing in Semiconductors

Abstract

Superconducting layers in silicon and germanium are fabricated via gallium implantation through a thin SiO2 cover layer and subsequent rapid thermal annealing. Gallium accumulation at the SiO2/Si and SiO2/Ge interfaces is observed but no pure gallium phases were found. In both cases superconducting transition occurs around 67 K which can be attributed to the metallic conducting, gallium rich interface layer. However, the superconducting as well as the normal-state transport properties in gallium overdoped silicon or germanium are dierent.

Pulsed Laser Annealed Ga HyperdopedPoly‐Si/SiOxPassivating Contacts for High‐Efficiency Monocrystalline Si Solar Cells

“…The maximum solid solubility limit of Ga in monocrystalline Si has been reported as 4 × 10 19 cm −3 at 1200 °C by Trumbore in 1959, [36] and the solid solubility limit is often lower (for example, 1 × 10 19 cm −3 at common cell processing temperatures of ∼900 °C [37] ). However, doping concentrations >10 20 cm −3 are desired for various applications, such as shallow p + junction, [38,39] superconducting semiconductors, [40][41][42] and low contact resistivity p-type contacts for solar cells. [32,43] Conventional thermal processes cannot reach a high level of doping concentration, so to overcome the equilibrium solid solubility limit, some early studies in the 1980s based on non-equilibrium processes have shown supersaturated Ga in silicon with a substitutional doping level of 1-8 × 10 20 cm −3 [44][45][46][47][48] as well as an active doping concentration of ∼3.5 × 10 20 cm −3 .…”