Hall-effect and resistivity measurements on semiconductors − implanted with radioactive ions − are able to reveal additional aspects of the material. Properties like resistivity and carrier concentration, which are measured by the corresponding non-nuclear method, are influenced by the time dependence of the nuclear decay. Implanted radioactive ions decay exponentially and may change their electrical behavior in the semiconductor if the doping characteristics of the new atoms are different. Thereby: the macroscopic quantities resistivity and carrier concentration change.
Thus these measurements often provide useful information complementary to techniques like the Perturbed Angular Correlation (PAC) for the investigation of defects in semiconductors. Nevertheless, the results of such Radio-Hall Effect measurements are interesting in their own right.
Hall effect and resistivity measurements were performed on n-type GaN implanted with 111In (→ 2.8d → 111Cd) in order to study the doping-characteristics of Cd in GaN. 111In which is expected to become incorporated on the Ga sub-lattice during the annealing procedure and there decays to Cd.
The samples (hexagonal n-type GaN n < 6.5·1012 cm-2) were implanted with 111In at total doses of 1·1012 cm-2 to 2·1012 cm-2 .The 111In-implantations have been performed at 160 keV. Additional implantations have been performed with stable 113In at the small dose of 1·1011 cm-2.
The hall- and resistivity measurements on these samples didn't show any time-dependent characteristics. The acceptor-levels seems to be deep in the large band-gap (3.6 eV). We continued with temperature-dependent measurements of the resistivity to examine the Cd-levels. There was a significant difference between the 111In- and the 113In-implanted samples. The much higher dose of the radioactive implantation seems to be responsible for that effect. Further investigations are necessary on this material.