Electrical isolation of GaAs by light ion irradiation damage

The electrical isolation in GaAs formed by light ion irradiation was systematically investigated. The threshold dose (D th) to convert a conductive layer to a highly resistive one is found to correlate with the doping level of the layer to be isolated and with the mass of the ion used. From the analysis of the obtained data it was deduced that the carriers are trapped by the antisite defects and/or their related defect complexes created in the collision cascades. The thermal stability of the isolation, i.e. the temperature range for which the sheet resistrance (R s) is maintained at ≈ 109 Ω/□, was found to be dependent on the ratio of the carrier trap concentration to the original carrier concentration. The temperature of ≈ 650°C is the upper limit for the thermal stability. A procedure is proposed for the design of the irradiation parametes to obtain improved thermal stability.