Evidence of boron pairs in highly boron laser doped silicon

TL;DR

This study investigates ultra-high boron doping in silicon using laser doping and mass spectrometry, revealing boron pair formation as a key factor affecting doping efficiency at high concentrations.

Contribution

It provides experimental evidence of boron pair formation in highly boron-doped silicon, highlighting its impact on doping activity and carrier concentration.

Findings

Boron concentration increases linearly with process repetitions.

Hole concentration saturates at high boron levels.

Boron and hole concentration difference scales with the square of boron concentration.

Abstract

Secondary Ions Mass Spectroscopy and Hall effect measurements were performed on boron doped silicon with concentration between 0.02 at.% and 12 at.%. Ultra-high boron doping was made by saturating the chemisorption sites of a Si wafer with BCl3, followed by nanosecond laser anneal (Gas Immersion Laser Doping). The boron concentration varies thus nearly linearly with the number of process repetitions. However, it is not the case for the hole concentration which tends to saturate at high boron concentration. The difference between boron and hole concentration increases as the square of boron concentration, pointing towards the formation of boron pairs as the dominant contribution to the increase of inactive boron.