9303764 Collins Based on the low leakage, room temperature detector performance demonstrated in a successful Phase I program, AstroPower is proposing further development of gallium phosphide detectors for nuclear particle detection under operating conditions of room temperature or above. The Phase II program will focus on developing and integrating the Phase I findings into high performance detectors. The detectors designs that will be developed can be used in three different room temperature device configuration: (i) a single junction low energy spectrometer or high energy encounter, (ii) a single junction, thin {SYMBOL 68 \f "Symbol"}{SYMBOL 69 \f "Symbol"} detectors, and (iii) a multiple junction medium to high energy spectrometer. These devices require the development of epitaxial growth techniques that yield high resistivity, thick layers with high crystalline perfection, and the development of processing techniques that yield high diode breakdown voltages. An important objective of this is to determine the specific energy range capabilities of GaP. It is expected that gallium phosphide will be a superior replacement for silicon and germanium for a wide energy range of protons, alpha particles and photons in harsh environments.