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

Abstract

The mean energy necessary to generate an electron-hole pair in gallium arsenide by x and γ 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 ε=4.216 eV has been measured at 300 K, lower than previously published values of 4.35 and 4.27 eV for α 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 ε=4.184±0.025 eV at 300 K. The dependence of ε on the temperature, in the 230–320 K range, has been found linear, ε=4.55−0.00122×T [eV]. The dependence of ε on the band gap has been determined ε=2.76×Eg+0.257 [eV], in good agreement with the Shockley-Klein theory. At 300 K, the found value of ε in GaAs, together with those reported for germanium and silicon, yields a linear dependence of ε on the band-gap energy ε=1.83×Eg+1.6 [eV], with a correlation coefficient of 0.9997.

Temperature dependence of the average electron-hole pair creation energy in Al0.8Ga0.2As

“…13 of Ref. 20 to show that plotting the electron-hole pair creation energies for Ge, Si, GaAs (and now Al 0.8 Ga 0.2 As) against their respective bandgap energies at 300 K yields a straight line (e ¼ 1:5453E g þ 1:8548 ½eV ) with a remarkably good fit (R 2 > 0.99) (Fig. 2).…”

“…Had there been significant incomplete charge collection, which would have adversely affected the determination of e AlGaAs , the data in Figure 1 would have shown significant non-linearity because of CCE's dependence on multiple temperature sensitive factors. 20 The change in average energy consumed in the generation of electron-hole pairs with temperature in Al 0.8 Ga 0.2 As is significant over the measured range: at 342 K it takes only $88% of the energy it does at 261 K to generate an electron hole pair on average. In context, assuming a temperature invariant F ¼ 0.12, this means the intrinsic spectral resolution (FWHM, Eq.…”

“…The gradient of the line of best fit representing the temperature dependence of the electron-hole pair creation energy in Al 0.8 Ga 0.2 As (À0.0077 eV/K, equivalent to À0.145% K À1 ) measured with 5.9 keV X-rays is much steeper than that reported for GaAs (À0.00122 eV/K, equivalent to À0.029% K À1 ) measured at 59.54 keV using 241 Am sources. 20 Both e GaAs and e Al0.8Ga0.2As have temperature gradients steeper than e Si which has been reported as $0.01% K À1 at very soft X-ray energies (50, 277, and 1800 eV) for temperatures between 308 K and 170 K. 21 It would be interesting to compare the temperature dependence of e Al0.8Ga0.2As with the temperature dependence of the material's bandgap energy, E g , but no compelling measurements of E g with temperature exist for Al 0.8 Ga 0.2 As. The same can be said for the temperature dependence of the F in Al 0.8 Ga 0.2 As.…”

Gallium arsenide 55Fe X-ray-photovoltaic battery

“…Because of the combination of built-in and applied electric field, electrons and holes in the depletion region accelerate in opposite directions and are swept to the p þ -type and n þ -type regions, respectively, generating a photocurrent. The average energy consumed in the generation of an electron-hole pair is called the electron-hole creation energy (4.18 eV for GaAs 19 ).…”

“…9 In contrast with what may have been expected, the experimental short circuit current (I SC ) magnitude decreases with increasing temperature. Because of the greater average energy consumed in the generation of an electron-hole pair (electronhole creation energy) at low temperatures, 19 less current may have been expected at low temperatures compared with high temperatures. The different behaviours observed may have been attributed to the increased electron mobility at lower temperatures.…”