Ionization coefficients in AlxGa1-xAs (x=0-0.60)

lonization coefficients are deduced from photomultiplication measurements o n a wide range of AlxGa1-xAs (x = 0-0.60) structures where the high-field r egion thicknesses vary from >1 mu m down to 0.05 mu m. Despite the dead spa ce becoming an increasing fraction of the device thickness as the thickness reduces, these coefficients implicitly include its effect such that they c an be used within the simple local ionization model to quantify the avalanc he processes in depletion regions as thin as 0.1 mu m. This success is attr ibuted to the fact that only a limited range of devices with comparable geo metries access the same high electric field when the dead space becomes sig nificant. An 'effective' or averaged coefficient can therefore be defined f or the devices which access this field. The presented coefficients render m ore complex models unnecessary for most multiplication calculations.