Anisotropic charge carrier transport in free-standing hexagonal boron nitride thin films

The in-plane and out-of-plane mobility-lifetime products of electrons and holes in free-standing hexagonal boron nitride (hBN) films are extracted from current-voltage characteristics of metal-hBN-metal structures measured under external excitations. The in-plane mobility-lifetime products for electrons and holes are similar to 2.8 x 10(-5) and similar to 4.85 x 10(-6) cm(2)/V, measured from lateral carrier collection, whereas the out-of-plane mobility-lifetime products for electrons and holes are similar to 5.8 x 10(-8) and similar to 6.1 x 10(-9) cm(2)/V, measured from vertical carrier collection, respectively. The mobility-lifetime product is a few orders of magnitude higher along the plane than along the out of plane in hBN films. (C) 2016 The Japan Society of Applied Physics