Boron redistribution in doping superlattices grown by silicon molecular beam epitaxy using B2O3

Abstract

Coevaporation of B₂O₃ during silicon molecular beam epitaxy has been used to prepare heavily doped superlattices (pipi’s). Full activation up to 3×10²⁰ cm⁻³ (100 times the solid solubility limit) was obtained at growth temperatures below 700 °C. Significant boron redistribution has been observed into the undoped layers when the dopant level in the intentionally doped layers exceeds the solid solubility limit and the growth temperature is greater than 700 °C. Oxygen was not incorporated into the lattice for growth temperatures above 700 °C when using B₂O₃ as the source of boron, a Si growth rate for 0.5 nm s⁻¹, and a B₂O₃ arrival rate of ∼2×10¹³ cm⁻² s⁻¹.