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

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