In thisstudy ,weprepareahigh-quality203μm-thick hexagonalboron nitride (h- BN) ( which is neuron-sensitive) using low-pressure chemical vapor deposition at 1 673 K ,achieving a growth rate of approximately 20 μm/h. We fabricate h-BN neutron detectors with vertical structuresbydepositing100nm-thick Au electrodeson both sidesofh-BN. Ourelectrical transport measurement results show that the prepared h-BN material possesses a mobility-life product (μτ) and resistivity of 2. 8 × 10- 6 cm2/V and 1. 5 × 1014 Ω · cm ,respectively. The neutron detectorbased on the203μm-thick h-BN exhibits neutron detection and charge collection efficiencies of34. 5% and 60% ,respectively ,at850V when irradiated by thermalneutrons from Am-Be sources.