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Non-Equilibrium Doping of Poly-Si:Ga/SiOx Passivating Contacts Solar Cells

Conference ·
DOI:https://doi.org/10.1063/5.0093805· OSTI ID:1889660
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In this contribution, we show that Ga-hyperdoped poly-Si/SiOx contacts are realized by pulsed laser annealing and post-hydrogenation. The motivation behind this work is to improve the inferior performance of boron-doped poly- Si/SiOx contacts when compared to the phosphorus-doped contacts. Here we used Ga as a novel p-type dopant to replace B, as B is known to accumulate at the interface between the oxide and the crystalline silicon and cause recombination. Due to a high diffusivity of Ga in oxide and a much higher segregation coefficient (Si:SiOx), Ga is shown to be immune to the oxide pileup phenomenon. However, Ga has a low solid solubility limit in Si (5x10^19 cm-3), which is not enough to form a low resistivity contact. To overcome this problem, we explored pulsed laser annealing via excimer laser by varying the laser energy densities and pulses. The passivation and electrical properties are studied systematically using photoluminescence (PL), secondary ion mass spectrometry (SIMS), and Van der Pauw-Hall measurements. We show an active Ga doping concentration above 1x10^20 cm^-3, which is above the solid solubility limit of Ga in Si. Good passivation quality is demonstrated with the highest implied Voc (iVoc) of 721 mV on single side polished samples. Furthermore, a low diode contact resistivity of ~22 m..omega.. cm^2 is obtained using Ti/Ag contacts, with minimal metal-to-semiconductor contact resistivity of 0.9 m..omega.. cm^2.
Research Organization:
National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
DOE Contract Number:
AC36-08GO28308
OSTI ID:
1889660
Report Number(s):
NREL/JA-5900-79755; MainId:36975; UUID:496b1f8b-69c5-4a43-bcce-fd9c020f97a7; MainAdminID:62930
Country of Publication:
United States
Language:
English

References (6)

An accurate calculation of spreading resistance journal April 2006
An Expanded Cox and Strack Method for Precise Extraction of Specific Contact Resistance of Transition Metal Oxide/ n- Silicon Heterojunction journal July 2019
Dopant distribution in gate electrode of n- and p-type metal-oxide-semiconductor field effect transistor by laser-assisted atom probe journal July 2009
Studying dopant diffusion from Poly-Si passivating contacts journal September 2019
Gallium-Doped Poly-Si:Ga/SiO2 Passivated Emitters to n-Cz Wafers With iV oc >730 mV journal November 2017
Bias temperature instability in scaled p/sup +/ polysilicon gate p-MOSFET's journal May 1999

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Related Subjects

SOLAR ENERGY
non-equilibrium doping
passivating contact
photovoltaic
poly Si/SiOx
solar cell