Fabrication of n+-poly-Si/p+-c-Si tunnel diode using Low-pressure Chemical Vapor Deposition for Photovoltaic Applications

Abstract

In this paper, an n+-poly-silicon/p+-crystalline-silicon tunnel diode has been fabricated and characterized. The n+ poly-silicon layer is deposited by the low-pressure chemical vapor deposition method, while a diffusion furnace is used for boron diffusion in crystalline silicon. Scanning electron microscopy and X-ray diffraction pattern have been used for structural characterization. Hall measurement and current-voltage characteristics have been used for carrier density, mobility, current density, and contact resistance measurement. Hall measurement reveals the carrier density of ~1019 cm-3 in phosphorus-doped poly-silicon tunnel layer with mobility of ~5.4 cm2 V-1-s-1. The current-voltage characteristics of the tunnel diode show the current density of ~103 Ampere/cm2 at a voltage of 0.1 Volt. Using tunnel diode, an n+-poly-Si/p+-c-Si/n-c-Si/n+-c-Si structure has been fabricated for photovoltaic application. This structure generates a current density of ~17.9 mA/cm2 and a voltage of 601 mV for a 195±10 nm thick doped poly-silicon layer. Further, to improve the solar cell’s performance, a thin layer of poly-silicon has been used.