Description:
The space dependence of the effective mass in heterostructures might lead to a strong interdependence of the longitudinal and transverse motion in systems with heterointerfaces, such as quantum wells. Such interdependence results in additional nonparabolicity of the longitudinal motion in quantum wells. At large energies, comparable to or exceeding the depth of a quantum well, the effective mass changes sign and the longitudinal two-dimensional spectrum terminates at a certain critical value of the longitudinal momentum. The space dependence of the effective mass also strongly increases the transmission through a potential barrier for electrons with large incidence angles. These effects should have important consequences for impact ionization and tunneling phenomena in GaN-based heterostructures.