Boron Phosphide Films by Reactive Sputtering: Searching for a P‐Type Transparent Conductor. Issue 12 (27th February 2022) - Crovetto, Andrea
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 × 10 20 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. Abstract : Boron phosphide (BP) holds promise as an unconventional p‐type transparent conductor. This work employs carbon doping and annealing of reactively sputtered BP films to achieve bipolar conductivity and the highest p‐type carrier concentration reported to date. Modifications to the deposition process are suggested to obtain better transparency and higher hole mobilities.