Boron-doping of cubic SiC for intermediate band solar cells: a scanning transmission electron microscopy study

TL;DR

This study investigates how boron precipitates and diffuses in cubic silicon carbide at high temperatures, revealing mechanisms that influence its potential for intermediate band solar cell applications.

Contribution

It provides detailed microscopic insights into boron precipitation behavior and solubility limits in 3C-SiC, informing doping strategies for solar cell efficiency.

Findings

Boron forms B13C2 precipitates in 3C-SiC at high temperatures.

Precipitates trap boron up to 1773 K, affecting doping levels.

High-temperature annealing increases boron solubility and diffusion.

Abstract

Boron (B) has the potential for generating an intermediate band in cubic silicon carbide (3C-SiC), turning this material into a highly efficient absorber for single-junction solar cells. The formation of a delocalized band demands high concentration of the foreign element, but the precipitation behavior of B in the 3C polymorph of SiC is not well known. Here, probe-corrected scanning transmission electron microscopy and secondary-ion mass spectrometry are used to investigate precipitation mechanisms in B-implanted 3C-SiC as a function of temperature. Point-defect clustering was detected after annealing at 1273 K, while stacking faults, B-rich precipitates and dislocation networks developed in the 1573 - 1773 K range. The precipitates adopted the rhombohedral B13C2 structure and trapped B up to 1773 K. Above this temperature, higher solubility reduced precipitation and free B diffused out of the implantation layer. Dopant concentrations E19 at.cm-3 were achieved at 1873 K.