Avalanche multiplication characteristics of Al/sub 0.8/Ga/sub 0.2/As diodes

The avalanche multiplication characteristics of Al/sub 0.8/Ga/sub 0.2/As have been investigated in a series of p-i-n and n-i-p diodes with i-region widths, w, varying from 1 /spl mu/m to 0.025 /spl mu/m. The electron ionization coefficient, /spl alpha/, is found to be consistently higher than the hole ionization coefficient, /spl beta/, over the entire range of electric fields investigated. By contrast with Al/sub x/Ga/sub 1-x/As (x/spl les/0.6) a significant difference between the electron and hole initiated multiplication characteristics of very thin Al/sub 0.8/Ga/sub 0.2/As diodes (w=0.025 /spl mu/m) was observed. Dead space effects in the diodes with w/spl les/0.1 /spl mu/m were found to reduce the multiplication at low bias below the values predicted from bulk ionization coefficients. Effective /spl alpha/ and /spl beta/ that are independent of w have been deduced from measurements and are able to reproduce accurately the multiplication characteristics of diodes with w/spl ges/0.1 /spl mu/m and breakdown voltages of all diodes with good accuracy. By performing a simple correction for the dead space, the multiplication characteristics of even thinner diodes were also predicted with reasonable accuracy.