Enhanced p-type conductivity and band gap narrowing in heavily B-doped p-BaSi2 films grown by molecular beam epitaxy

摘要

B-doped p-BaSi2 layers growth by molecular beam epitaxy and the effect of rapid thermal annealing (RTA) on hole concentrations were presented. The influence of B-doping on band gap shrinkage was also addressed. The hole concentration was controlled in the range between 10¹⁷ and 10²⁰ cm⁻³ at room temperature by changing the temperature of the B Knudsen cell crucible. The acceptor level of the B atoms was estimated to be approximately 23 meV. High hole concentrations exceeding 1×10²⁰ cm⁻³ were achieved via dopant activation using RTA at 800 °C in Ar. By using this optimized growth condition the absorption edge of the B-doped p-BaSi2 on the Silicon-on-insulator substrate was found to be about 1.23 eV, and it's giving 0.1 eV shrinkage of energy band gap of B-doped BaSi2. The novel p⁺-layer is an important achievement towards p-n junction BaSi2 solar cells.