Non-local effects on the multiplication characteristics of thin GaAs p-i-n and n-i-p diodes

Electron and hole multiplication characteristics have been measured on a series of GaAs p-i-n and n-i-p diodes in which the nominal i-region thicknesses, w, range from 1 μm to 25 nm. Using the conventional analysis, where ionization is assumed to be uniform across the device, the effective electron and hole ionization coefficients (α and β respectively) have been deduced. The results obtained from the w=1 μm and 0.5 μm structures agree with published data which was derived from thick devices. However, those observed in the thinner structures show device width dependence. By implementing semi-analytical techniques to solve Boltzmann´s equation and to interpret these results, dead space effects are seen to reduce α and β in short devices at low multiplication values but overshoot effects compensate when the electric field is increased