An apparatus comprising at least one multilayer wafer which includes a device layer adjacent to a barrier layer, and the device layer includes at least two photoconductive regions separated by an etched channel extending through the device layer. In some instances the apparatus may be an accelerometer having two photodiodes formed on a silicon-on-insulator (SOI) wafer with the photodiodes defined by one or more etched channels extending through the device layer of the SOI wafer. Also disclosed are methods for forming such an apparatus.