THE EFFECT OF STRAIN-INDUCED POLARIZATION-FIELDS ON IMPACT IONIZATIONIN A MULTI-QUANTUM-WELL STRUCTURE

We present a mechanism for enhancing the electron impact ionization ra te based on the strain-induced polarization fields in a strained multi quantum-well system. To illustrate the concept, the electron ionizatio n rate is calculated for a strained GaN and Al0.3Ga0.7N multiquantum-w ell device. The presence of the polarization fields within the Al0.3Ga 0.7N layers provides an additional mechanism for carrier heating to th e conduction band edge discontinuity of earlier simple multiquantum-we ll 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. (C) 1998 American Institute o f Physics. [S0003-6951(98)01445-4].