Boron doping in Si molecular beam epitaxy by co-evaporation of B2O3 or doped silicon

Abstract

We report on controlled boron doping of silicon molecular beam epitaxy (MBE) films by two techniques: sublimation of saturated boron‐doped silicon from a boron nitride crucible and evaporation of B₂O₃ from a tungsten crucible. Both methods were performed with the simultaneous evaporation of undoped silicon from an electron beam source. Sharp doping profiles and constant evaporation rates were obtained for both methods. Doping levels between 2×10¹⁷ and 1.5×10²⁰ cm⁻³ were realized. The evaporations require only relatively low temperatures: 700–1150 °C for B₂O₃ and 1000–1400 °C for subliming silicon. These results make it possible to replace gallium as the p‐type evaporative dopant in silicon MBE with the more desirable boron without using ion imbedding or a very high crucible temperature.