The effect of strain-induced polarization fields on impact ionization in a multiquantum-well structure

We present a mechanism for enhancing the electron impact ionization rate based on the strain-induced polarization fields in a strained multiquantum-well system. To illustrate the concept, the electron ionization rate is calculated for a strained GaN and Al0.3Ga0.7N multiquantum-well device. The presence of the polarization fields within the Al0.3Ga0.7N layers provides an additional mechanism for carrier heating to the conduction band edge discontinuity of earlier simple multiquantum-well avalanche photodiode designs. It is found that the ionization rate is substantially enhanced over both its bulk GaN value and that for an unstrained multiquantum-well structure.