Experimental investigation of 200 MeV Ag-107(14+) ion induced modifications in n-GaAs epitaxial layer by in situ resistivity and Hall measurements

Gallium arsenide (GaAs) grown by metallorganic chemical vapor deposition (M OCVD) method and n-doped with silicon to a concentration of 4 x 10(17) cm(- 3) was exposed to 200 MeV Ag-107(14+) ion irradiation. The ion fluence was varied from 2 x 10(8) to 5 x 10(11) ions cm(-2). The modifications in elect rical transport behavior of n-GaAs epitaxial layer was studied by employing in situ resistivity and Hall measurements. The resistivity exhibited a slo w increase upto a fluence of 1 x 10(10) ions cm(-2), and then increased in a quasi-exponential manner with respect to fluence. The free carrier concen tration in the epitaxial layer, as calculated from Hall measurements, initi ally showed a slow decrease until a fluence of 1 x 10(10) ions cm(-2) is re ached. After this fluence, the free carrier concentration decreased quickly with increase in fluence. The carrier mobility also exhibited a similar ki nd of trend. The observed modifications in transport properties have been e xplained on the basis of production of defects in n-GaAs epitaxial layer by swift heavy ion irradiation and the resultant trapping of free carriers. ( C) 2001 Published by Elsevier Science B.V.