Electrical isolation of n-type and p-type InP layers by proton bombardment

The evolution of the sheet resistance (R-s) of n-type and p-type conductive InP layers during proton irradiation and the stability of the formed isolation during postirradiation annealing were investigated. It was found that the threshold dose (D-th) to convert the conductive layer to a highly resistive one is different for n- and p-type samples with similar initial free carrier concentrations. From our results, one infers that the antisite defects and/or related defect complexes formed by the replacement collisions are the carrier trapping centers, where In-P is responsible for electron trapping and P-In for the hole trapping. A time dependence of the R-s was observed after each irradiation step to doses of congruent toD(th) and higher. This time variation is related to metastable processes involving free carriers. The thermal stability of the isolation of n-type samples is limited to temperatures lower than 200 degreesC, irrespectively of the irradiated dose. For p-type samples the thermal stability of electrical isolation is extended to 450-500 degreesC. (C) 2001 American Institute of Physics.