The electron impact ionization coefficient in a GaAs-Ga0.7 Al0.3As multiple quantum well structure

The electron ionization coefficient (α) is experimentally measured in a p-i-n diode structure with a multiple quantum well (MQW) `i´ region as the well and barrier dimensions are systematically varied. Assuming that α⩾β (hole ionization coefficient) it is shown that α can be obtained accurately for low electric-fields if only the electron initiated multiplication is known. A number of structures are grown with 100 Å wells and Ga_0.7Al_0.3As barriers varying in thickness from OÅ (bulk GaAs) to 60 Å. In all the structures considered α is found to be less than that for GaAs and similar to that for a uniform GaAlAs alloy obtained by complete intermixing of the wells and barriers