Donor and acceptor levels in impurity-doped semiconducting BaSi2 thin films for solar-cell application

Abstract

Identification of donor and acceptor energy levels in BaSi2 due to the suitable impurity injection of different types is very essential for the design and development of heterojunction or homojunction solar cells. In this article, donor and acceptor energy levels due to the impurity Sb-, In-, Ga-, Cu-, Al-, Ag-, P-, and B-doped BaSi2 films grown by molecular beam epitaxy (MBE) were investigated. It was found that impurity Sb-, Ga-, Cu-, and P-doped BaSi2 exhibited n-type conductivity, while impurity In- Al-, Ag-, and B-doped BaSi2 exhibited p-type conductivity, using the Van der Pauw method at room temperature (RT). The temperature dependence of electron or hole concentrations indicated that the acceptor energy levels in impurity B-, In-, Ag-, and Al-doped BaSi2 are 23, 86, 126, and 140 meV, respectively, and the donor energy levels in impurity Cu-, Sb-, P-, and Ga-doped BaSi2 are 35, 47, 80, and 120 meV, respectively. The shallow acceptor level of 23 meV in p-type BaSi2 due to B impurity atoms and two novel donor levels of 47 and 35 meV, respectively, due to Sb and Cu impurity atoms in n-type BaSi2 were successfully identified for photovoltaic applications.