Experimental investigation of 200 MeV 107Ag14+ ion induced modifications in n-GaAs epitaxial layer by in situ resistivity and Hall measurements

Gallium arsenide (GaAs) grown by metallorganic chemical vapor deposition (MOCVD) method and n-doped with silicon to a concentration of 4×1017 cm−3 was exposed to 200 MeV 107Ag14+ ion irradiation. The ion fluence was varied from 2×108 to 5×1011 ions cm−2. The modifications in electrical transport behavior of n-GaAs epitaxial layer was studied by employing in situ resistivity and Hall measurements. The resistivity exhibited a slow increase upto a fluence of 1×1010 ions cm−2, and then increased in a quasi-exponential manner with respect to fluence. The free carrier concentration in the epitaxial layer, as calculated from Hall measurements, initially showed a slow decrease until a fluence of 1×1010 ions cm−2 is reached. After this fluence, the free carrier concentration decreased quickly with increase in fluence. The carrier mobility also exhibited a similar kind of trend. The observed modifications in transport properties have been explained on the basis of production of defects in n-GaAs epitaxial layer by swift heavy ion irradiation and the resultant trapping of free carriers.