  Weak antilocalization is studied in an InGaAs quantum well. Anomalous
magnetoresistance is measured and described theoretically in fields
perpendicular, tilted and parallel to the quantum well plane. Spin and phase
relaxation times are found as functions of temperature and parallel field. It
is demonstrated that spin dephasing is due to the Dresselhaus spin-orbit
interaction. The values of electron spin splittings and spin relaxation times
are found in the wide range of 2D density. Application of in-plane field is
shown to destroy weak antilocalization due to competition of Zeeman and
microroughness effects. Their relative contributions are separated, and the
values of the in-plane electron g-factor and characteristic size of interface
imperfections are found.
