Hole currents are observed by illuminating 2,3 DN single crystals with 347 nm and 337 nm. The probability of generating free holes is a function of temperature and electric field-strength. In the cleavage plane of the crystals the mobility does not depend on the direction of the applied field and amounts to 2.6·10-1 cm2/Vsec at room temperature, which exceeds the related value measured perpendicularly to the plane by a factor of four. The temperature-dependence of the mobility indicates shallow hole-trapping exspecially close to the surface. The trap depth is estimated to be 10-2 eV. Temperature also influences the pulse shape, by which one can conclude that hole traps of 0.2 eV and ≲ 0.1 eV exist in a thin surface layer. Photocurrents exited with 347 nm increase stronger than quadratically with the electric field. Deep hole traps, being also restricted to the surface region of the crystals, are made responsible for this fact.