NEW BISTABLE DEFECT WITH DEEP LEVELS IN SI-DOPED ALXGA1-XAS

A new bistable defect, not associated with a DX center, has been observed in an epitaxial layer of n-type Al0.3Ga0.7As grown by organometallic hydride chemical vapor deposition. Measurements were carried out by the C-V and DLTS methods at a gold Schottky barrier after a preliminary isochronous, isothermal annealing in two cooling regimes: one with a zero bias voltage U0 = 0 and one with a reverse bias voltage U0 < 0. A stable state of the bistable defect, with a thermal-activation energy E1 = E(c) - 165 meV and an electron capture cross section sigma(n) = 1.07 x 10(-13) cm-2, is observed during an isochronous annealing at U0 = 0. This level has properties similar to those of the E1 level which forms during irradiation of Al0.3Ga0.7As. It is associated with a V(As) defect. During an isochronous annealing at U0 < 0, a metastable level of the bistable defect with E2 = E(c) - 208 meV and sigma(n) = 2.54 x 10(-14) cm2 is observed. The results show that the defect transformation E1 --> E2 has a first-order kinetics and is caused by two traps, E2 and E2*, which are annealed out at different rates. It is suggested that this defect is a complex consisting of an arsenic vacancy and an impurity.