n+p Junctions in p-type c-Ge based on annealed phosphorous-doped nanocrystalline silicon films
Year: 2025
Type: article
Abstract: Crystalline germanium (c-Ge) substrates epitomize a cost-effective approach in the development of many optoelectronic technologies requiring low bandgap materials such as thermophotovoltaic cells and infrared photodetectors. However, high quality junction formation in these devices is mostly based on epitaxial growth of III-V semiconductors, which jeopardizes the low-cost approach, or silicon heterojunctions requiring complex surface preparations. In this work, we demonstrate an alternative approach for n+/p junctions by furnace annealing (~700 ºC) phosphorous-doped nanocrystalline silicon (nc-Si(n)) films deposited by PECVD. ToF-SIMS measurements reveal silicon and phosphorous diffusion into the c-Ge bulk after the annealing, while Raman spectroscopy indicates the formation of a crystalline SiGex alloy at the interface. Under optimized annealing conditions, the junction exhibits low hole saturation current densities of 1-2µA/cm2 and sheet resistances of the n-type region below 50 Ω/sq. We incorporate the junction into a proof-of-concept photovoltaic device whose temperature-dependent J-V measurements indicate a hole current flow with an ideality factor of 1 and an activation energy of 0.79 eV, consistent with recombination in the quasi-neutral region of the diffused SiGex alloy. The obtained efficiency (6.29 % under AM1.5g illumination) highlights the potential of this non-epitaxial process for high-quality electron-selective contacts in germanium photovoltaics.
Source: Applied Surface Science
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,930
OpenAlex ID: W4414606524