Electron-hole pair generation energy in gallium arsenide by x and γ photons

The mean energy necessary to generate an electron-hole pair in gallium arsenide by x and gamma photons has been measured in the 230-320 K temperature range. The experimental apparatus consists of a Schottky junction on a high-quality epitaxial GaAs, a silicon detector that generates a reference charge signal and highly stable low-noise electronics. The resolution of the system in measuring the generation energy is better than 2 meV. An apparent value of epsilon=4.216 eV has been measured at 300 K, lower than previously published values of 4.35 and 4.27 eV for alpha particles and 4.57 eV for electrons. Charge trapping in the GaAs detector, although very weak (less than 1%), has been observed and a model, based on the Hecht theory, has been developed to derive the true value of epsilon=4.184+/-0.025 eV at 300 K. The dependence of epsilon on the temperature, in the 230-320 K range, has been found linear, epsilon=4.55-0.00122xT [eV]. The dependence of epsilon on the band gap has been determined epsilon=2.76xE(g)+0.257 [eV], in good agreement with the Shockley-Klein theory. At 300 K, the found value of epsilon in GaAs, together with those reported for germanium and silicon, yields a linear dependence of epsilon on the band-gap energy epsilon=1.83xE(g)+1.6 [eV], with a correlation coefficient of 0.9997. (C) 2002 American Institute of Physics.