Average energy needed to produce an electron-hole pair in GaSe nuclear particle detectors

Gallium selenide (GaSe) detectors, which were fabricated by evaporating small electrodes of various metal films (Au, Al, In, In+Hg, Ag, and Sn) onto 50- to 150- mu m-thick plates cleaved from Bridgman-grown crystals, have been tested. One detector exhibited pulse heights that corresponded to 4.5 eV, possibly 4.0 to 4.3 eV, as an average energy necessary to produce an electron-hole pair for 5.5-MeV alpha-particle irradiation. These measured values are smaller than the 6.3 eV predicted by the Klein formula.<>