Lateral charge carrier transport properties of B-10 enriched hexagonal BN thick epilayers

Neutron detectors based on B-10 enriched hexagonal boron nitride (h-¹⁰BN or h-BN) epilayers have demonstrated the highest thermal neutron detection efficiency among solid-state neutron detectors at about 58%. However, many fundamental transport parameters of h-BN, including the room temperature carrier mobility, minority carrier lifetime, and surface recombination velocity, which are essential to the performance of detectors, are still unknown. We report here the carrier drift mobilities (μ) and lifetimes (τ) of both electrons and holes in h-¹⁰BN epilayers measured by using a time-of-flight (TOF) technique. Lateral photoconductive type detectors fabricated from a 65 μm thick freestanding h-¹⁰BN epilayer were utilized to carry out the TOF measurements, which revealed μ_e ∼34 cm²/V s for electrons and μ_h ∼36 cm²/V s for holes and carrier lifetimes on the order of tens of microseconds. By combining the values of μ measured from TOF with S/μ (the ratio of the surface recombination velocity to mobility) deduced directly from the bias voltage dependence of photocurrent, S for both electrons (S_e ∼1.4 × 10⁴ cm/s) and holes (S_h ∼2.7 × 10³ cm/s) in h-¹⁰BN has been extracted. The determination of these important fundamental parameters (μ, τ, and S) not only provides a better understanding of the carrier dynamics and electrical transport properties of h-BN but is also valuable for further advancing the development of h-BN materials and devices.