A study of electrical transport properties and detection performances of the semi-insulating InP-based detectors of charged particles and ionizing radiation is presented. Detectors with a top P+ layer and a Schottky back contact give a charge collection efficiency over 90% and energy resolution about 3% (FWHM) for 5.48 MeV α-particles at 220 K. Detection of 60, 122 and 662 keV γ-rays in a temperature range 215÷250 K is demonstrated
