Boosting Charge Carrier Mobilities in Upgraded Metallurgical Grade Silicon by Phosphorous Diffusion Gettering

Abstract

Herein, it is demonstrated how the carrier mobility and carrier lifetime of upgraded‐metallurgical grade silicon (UMG‐Si), a feedstock alternative to electronic‐grade, high‐purity polysilicon dominating photovoltaic technology, can be largely improved upon the gettering action of industrially compatible phosphorous diffusion gettering (PDG) process at the wafer level. The results, based on ultrafast THz spectroscopy and inductively coupled photoconductive decay measurements, show outstanding increments in the carrier lifetime of PDG‐treated multi‐crystalline UMG‐Si wafers from 50 ps to 25 μs and a boost in intra‐grain charge carrier mobility from 283 ± 37 up to 726 ± 23 cm2 Vs−1. Most remarkably, the latter figure parallels the carrier mobility observed in monocrystalline wafers manufactured from polysilicon, thereby demonstrating the effectiveness of a simple pre‐conditioning step in upgrading the electronic properties of UMG‐Si up to the device level.