Surface barrierp‐njunction diodes made from high‐purityn‐GaAs grown by liquid‐phase epitaxy, have been operated as &agr;‐particle and low‐energy &ggr;‐ray detectors over the range 77–373°K. Resolutions observed were 1.2 and 2.95 keV (FWHM) at 130 and 295°K, respectively, for 122‐keV &ggr; rays and 30 keV for 5.47‐MeV &agr; particles. The energy per electron hole pair for &agr; particles is 4.51 eV and the Fano factor for &ggr; rays is ≤0.24 at 130°K.