Control of hole concentration in sputter-deposited BaSi2 films by B implantation and its application to p-BaSi2/n-Si solar cells

Barium disilicide (BaSi2) has potential applications in thin-film solar cells; hence, it is important to control the carrier type and carrier concentration of BaSi2 films formed by large-area deposition techniques such as sputtering. However, neither n-type nor p-type impurity-doped BaSi2 films have been achieved by sputtering. In this work, we formed 0.2 mu m-thick BaSi2 films on Si(111) substrates by sputtering and achieved the control of hole concentration by ion implantation of B using BF3 and subsequent post annealing (PA) at 1000 degrees C in an Ar atmosphere. With a dose of 10(14) (10(15)) cm(-2), the hole concentration was increased continuously with increasing annealing duration (t(a)), reaching around 10(18) (10(19)) cm(-3) for t(a) > 4 min. This is the first demonstration of hole concentration control in sputter-deposited BaSi2 films. Both photoluminescence and Raman spectra revealed that the implantation damage was recovered by PA at t(a) approximate to 1 min. The operation of B-implanted p-BaSi2/n-Si heterojunction solar cells was also demonstrated.