A new bistable defect, not associated with a DX center, has been obser
ved in an epitaxial layer of n-type Al0.3Ga0.7As grown by organometall
ic hydride chemical vapor deposition. Measurements were carried out by
the C-V and DLTS methods at a gold Schottky barrier after a prelimina
ry 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 ener
gy 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 whi
ch forms during irradiation of Al0.3Ga0.7As. It is associated with a V
(As) defect. During an isochronous annealing at U0 < 0, a metastable l
evel 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 transfo
rmation E1 --> E2 has a first-order kinetics and is caused by two trap
s, E2 and E2, which are annealed out at different rates. It is sugges
ted that this defect is a complex consisting of an arsenic vacancy and
an impurity.