The use of fiber optics in the diagnosis of hostile nuclear environments has brought about a pressing need for the development of suitable radiation-to-light converters. These converters must meet stringent diagnostic requirements of linearity and time response while having a wavelength of emission that is compatible with transmission over relatively long lengths of optical fibers. Initial investigations of two, near-infrared-emitting semiconducting materials - CdTe and GaAs are described. Data are presented on the wavelength of emission, linearity, time response, and relative efficiency of these semiconductors. Most data were taken at 77 K because of a dramatic increase in efficiency at this temperature. Measurments show that the intensity-vs-dose curves are linear over several decades of useful input levels. Measurements indicate that GaAs has an efficiency and time response that promise to be useful in diagnostic systems.