Solid-state photon detectors based on wide band gap semiconductors are not yet considered mature technology but their current development opens new possibilities, also for space observations. Such devices are especially attractive for ultraviolet radiation detection, as semiconductor materials with band gaps larger than that of silicon can be produced and used as "visible-blind" or "solar-blind" detectors that are not affected by daylight. Here we evaluate the advantages of such detectors compared to silicon-based devices and report on the semiconductor detectors that have been fabricated in recent years with materials having large band gap energies. We describe the most common pixel designs and characterize their general properties.