Robert Gawron has been working on a semiconductor radioactivity detector project:
Currently I’m trying to make a working version of a radioactivity detector that uses semiconductor as a sensor. It’s a different approach than Geiger-Muller detectors, more complicated, but also much more interesting.
While Geiger-Muller counters can only provide information about the amount of particles in a period of time, semiconductor detectors can also measure their energy, so it’s possible to say much more about the nature of observed ionizing radiation. Some of the disadvantages of these detectors are that they are more expensive, complex and sensitivity may degrade over time.
More details at Robert Gawron’s blog.