Avalanche multiplication characteristics of Al0.8Ga0.2As diodes

The avalanche multiplication characteristics of Al0.8Ga0.2As have been inve stigated in a series of p-i-n and n-i-p diodes with i-region widths, w, var ying from 1 mum to 0.025 mum. The electron ionization coefficient, alpha, i s found to be consistently higher than the hole ionization coefficient, bet a, over the entire range of electric fields investigated. By contrast with AlxGa1-xAs (x less than or equal to 0.6) a significant difference between t he electron and hole initiated multiplication characteristics of very thin Al0.8Ga0.2As diodes (w = 0.025 mum) was observed. Dead space effects in the diodes with w less than or equal to 0.1 mum were found to reduce the multi plication at low bias below the values predicted from bulk ionization coeff icients. Effective alpha and beta that are independent of w have been deduc ed from measurements and are able to reproduce accurately the multiplicatio n characteristics of diodes with w greater than or equal to 0.1 mum and bre akdown voltages of all diodes with good accuracy. By performing a simple co rrection for the dead space, the multiplication characteristics of even thi nner diodes were also predicted with reasonable accuracy.