  Quantum nucleation processes in the presence of local moderate
inhomogeneities are studied theoretically at high biases. The quantum
nucleation rate Gamma is calculated for one-dimensional systems in a form Gamma
= A e^(-B/hbar) by using the `bounce' method. The bias-dependence of the
exponent B is shown to be changed by inhomogeneities. This change is explained
by the reduction of the effective spatial dimension of the system. By studying
the system-size dependence of the prefactor A, the condition for the appearance
of inhomogeneity effects is evaluated. Nucleation rates in thermal activation
regimes are also calculated, and compared with quantum tunneling regimes. For
higher-dimensional systems, it is shown that the local approximation of
inhomogeneity does not hold, and that spatial profiles of inhomogeneity become
important.
