Electrical isolation of AlxGa1-xAs by proton irradiation

The evolution of sheet resistance (R_s) of n-type and p-type conductive Al_xGa_1-xAs layers (x=0.3, 0.6 and 1.0) during proton irradiation was investigated. The threshold dose (D_th) to convert a conductive layer to a highly resistive one is slightly different for n- and p-type samples with similar initial free carrier concentration and does not depend on the Al content. The thermal stability of the isolation, i.e. the temperature range for which the R_s is maintained at ≈10⁹ Ω/sq, was found to be dependent on the ratio of the carrier trap concentration to the original carrier concentration. The thermal stability of isolated p-type samples is limited to temperatures lower than 450°C. The temperature of ≈600°C is the upper limit for the n-type samples thermostability.