A multilayer 
semiconductor scintillator is disclosed for detection, energy quantification, and determination to source of high-energy 
radiation, such as gamma or X-
ray photons or other particles that produce ionizing interaction in semiconductors. The basic embodiment of the inventive 
detector comprises a multiplicity of stacked direct-gap 
compound semiconductor wafers, such as InP and GaAs, each 
wafer heavily doped n-type so as to maximize its transparency to scintillating 
radiation. Each 
wafer is further endowed with surface means for detection of said scintillating 
radiation, such a hetero-epitaxial p-i-n 
photodiode. In a preferred embodiment, the 
photodiode layer in each 
wafer is pixellated so as to provide the x and y coordinates of an ionizing interaction event. Combined with the 
z coordinate provided by the wafer index in the stack, the inventive 
detector yields the three-dimensional coordinates of each ionizing interaction event associated with absorption of an individual 
quantum of high-energy radiation. This three-dimensional information enables a further disclosed advantageous 
analysis method that is suitable for 
rapid identification of radioactive isotopes and determination of the direction to the source of radiation.