DETERMINATION OF THE EL2 INTRODUCTION RATE AND FERMI-LEVEL SHIFT DUE TO PROTON AND PION IRRADIATION IN SEMIINSULATING GAAS

The bulk damage (namely the introduction rate of the arsenic antisite As-Ga and its ionisation ratio, the Fermi-level position and resistivi ty) was determined as a function of the non-ionising energy loss (NIEL ) of hadrons in semi-insulating (SI) GaAs, The study was performed usi ng near-infrared (NIR) absorption and time dependent charge measuremen ts (TDCM) on 23 GeV proton and 192 MeV pion irradiated Liquid Encapsul ated Czochralski (LEG) grown GaAs. We have shown that the bulk damage scales linearly with the total NIEL up to a pion fluence of 5 x 10(14) particles/cm(2) The EL2 introduction rate for the high energetic pion s and protons were determined to be 92.7 +/- 2.6 cm(-1) and 68.1 +/- 3 .7 cm(-1), respectively. A comparison of these values gives a hardness factor for the 192 MeV pions of 9.5 +/- 1.4. In addition it was found that the variation of the Fermi-level and resistivity with radiation damage is a function of the initial resistivity of the SI GaAs before irradiation. (C) 1998 Elsevier Science B.V.