Metastable defects in as-grown and electron-irradiated

New metastable defects have been observed in Si-doped layers, grown by MOCVD and irradiated with 1 MeV electrons in the dose range at T = 300 K. The investigations have been carried out by DLTS after preliminary isochronous and isothermal annealing with applied reverse bias voltage and at U = 0. In as-grown AlGaAs the stable-state parameters with a thermal activation energy and electron capture cross section were identical to those of the E1 defect formed under irradiation of AlGaAs and identified as . The parameters of the metastable state were and . The kinetics of configurational transformations of the defect was first-order. The thermal activation energy and the pre-exponential factor were and for the defect transition and and for the reverse transformation. The metastable defect is supposed to include and, possibly, a donor impurity. In irradiated material a rise in the concentration of metastable defects has been observed. As in as-grown AlGaAs, the signature of the stable state was identical to that of the E1 defect, but the transformation mechanism was changed, which is probably connected with the formation of another pair . The value of may correspond in order of magnitude to an interstitial single-jump process.