The role of the ohmic contact on the efficiency of gallium arsenide radiation detectors

It has recently been found that in gallium arsenide radiation detectors injecting ohmic contacts impede charge collection efficiency to get 100%, since breakdown occurs as soon as the electric field reaches the contact itself. In the present contribution, this phenomenon is investigated by comparing two sets of ohmic contacts realized by different technological procedures. While the overall defective state results to be nearly the same for both contacts, their performance significantly differs. Deep level junction spectroscopy shows that the defects are the same in both sets whilst there is much difference in density between a few of them.