Bulk Silicon Crystals with the High Boron Content, Si1–xBx: Two Semiconductors Form an Unusual Metal

Abstract

Silicon is a key technological material, and its controlled doping is one of the simple and effective ways which are applied for creation of new advanced materials with tunable optoelectronic properties. Boron was known to be a dopant that can dramatically change the properties of silicon. However, a limited solubility of boron atoms in silicon matrix strongly restricted creation of bulk diamond-type structured Si–B alloys with the high boron content exceeding 0.5–1 at. %. In this work we show that bulk Si1–xBx alloys with a rather high boron content (e.g., 2.4 at. %) may be fabricated by alloying of boron and silicon at high temperatures above the melting point of silicon and high pressure. We extensively investigated the electronic transport and optical properties of these alloys using several techniques, including electrical resistivity, Hall effect, magnetoresistance, Raman, IR and optical spectroscopy, and X-ray diffraction. We found that Si1–xBx solid solutions are metals that possess very unusual o...