Impact ionization in thin AlxGa1−xAs (x=0.15 and 0.30) p-i-n diodes

The electron and hole multiplication characteristics, $M_e$ and $M_h,$ respectively, have been measured in two series of ${\mathrm{Al}}_x{\mathrm{Ga}}_{\text{1−x}}^{}\mathrm{As}$ $\text{(x=0.15}$ and 0.30) p-i-n diodes where the $i$ -region thicknesses, $\mathrm{w,}$ vary from 1.0 down to 0.025 μm. From these, the effective electron and hole ionization coefficients, α and β, respectively, have been determined and in the thicker structures agreement is found with data published previously in the literature. However, in the devices where $\text{w⩽0.1}$ μm, the dead space effect reduces multiplication below their bulk values at lower values of bias. As the bias is increased, α and β increase very rapidly suggesting that overshoot effects are compensating for the dead space.