Crovetto, A.; Adamczyk, J.M.; Schnepf, R.R.; Perkins, C.L.; Hempel, H.; Bauers, S.R.; Toberer, E.S.; Tamboli, A.C.; Unold, T.; Zakutayev, A.: Boron Phosphide Films by Reactive Sputtering: Searching for a P-Type Transparent Conductor. Advanced Materials Interfaces 9 (2022), p. 2200031 / 1-11
10.1002/admi.202200031
Open Access Version
Abstract:
With an indirect band gap in the visible and a direct band gap at a much higher energy, boron phosphide (BP) holds promise as an unconventional p-type transparent conductor. This work reports on reactive sputtering of amorphous BP films, their partial crystallization in a P-containing annealing atmosphere, and extrinsic doping by C and Si. The highest hole concentration to date for p-type BP (5 × 1020 cm−3) is achieved using C doping under B-rich conditions. Furthermore, bipolar doping is confirmed to be feasible in BP. An anneal temperature of at least 1000 °C is necessary for crystallization and dopant activation. Hole mobilities are low and indirect optical transitions are stronger than that predicted by theory. Low crystalline quality probably plays a role in both cases. High figures of merit for transparent conductors might be achievable in extrinsically doped BP films with improved crystalline quality.