N-type heavy doping with ultralow resistivity in Ge by Sb deposition and pulsed laser melting

Abstract

The fabrication of highly doped and high quality Ge layers is a challenging and hot topic for advancements in nanoelectronics, photonics and radiation detectors. In this article, we report on a simple method for junction formation consisting in sputter depositing or evaporating a thin pure Sb layer on Ge followed by cycles of Pulsed Laser Melting (PLM). We show that PLM promotes an efficient diffusion of high Sb concentrations into the melted Ge subsurface layer, followed by a fast epitaxial regrowth. The resulting layer is perfectly pseudomorphic to the Ge substrate, preserving the high strain level induced by the Sb, having covalent radius higher than Ge. In addition, it shows extremely high active concentrations up to 3 × 1020 cm−3 and a record low resistivity of 1.4 × 10-4 Ohm cm. The carrier mobility is also in line with the extrapolation of literature data with no signs of mobility degradation. Furthermore, infrared reflectivity confirms the good optical quality of the doped layers and demonstrates, for the first time, plasma wavelengths in Ge below 3 µm. These results are highly relevant for nanolectronic and plasmonic applications.