Semi-3D detectors are similar to planar detectors but their surface is modified using electro-chemical etching into the shape of regular arranged pyramids, pillars or recess. Aim of this modification is to larger active surface area of the detector and use the conversion layer sensitive to thermal neutrons. Increasing the active area of the detector causes increased detection efficiency, which is confirmed by both numerical calculations and by experiments. Draft Semi-3D detectors in the shape of a pyramid is the original proposal of Dr. Pospíšil.
3D detectors proposed by S. Parker are new generation of semiconductor devices. Collecting electrodes, compared with previous types of semiconductor detectors are in form of very narrow cylinders penetrating through the entire thickness of the detector perpendicular to the surface. Electrodes are etched by electrochemical etching and doped with polykrystaline silicon. 3D detectors will therefore show short charge collection times and will provide very fast signals. It can be expected that both chracteristics will have a significant impact on improving the radiation hardness.