A new method to control impact ionization rate ratio by spatial separation of avalanching carriers in multilayered heterostructures

We propose a new scheme to control the impact ionization rate ratio α/β of electrons and holes by utilizing multilayered heterostructures (–A–B–A–B–). In the structure, avalanching carriers, which accelerated mainly along the layer plane, are spatially separated by the action of band edge discontinuities in such a way that the impact ionization process of electrons takes place mainly in layer A and that of holes in layer B. An analysis is made to show that a proper choice of constituent materials allows the control of α/β over an extremely wide range (10−2∼103).