Avalanche noise characteristics of single AlxGa1-xAs(0.3 < x < 0.6)-GaAs heterojunction APDs

Avalanche multiplication and excess noise have been measured on a series of AlxGa1-xAs-GaAs and GaAs-AlxGa1-xAs (x = 0.3, 0.45, and 0.6) single heterojunction p(+)-i-n(+) diodes. In some devices excess noise is lower than in equivalent homojunction devices with avalanche regions composed of either of the constituent materials, the heterojunction with x = 0.3 showing the greatest improvement. Excess noise deteriorates with higher values of x because of the associated increase in hole ionization in the AlxGa1-xAs layer. It also depends critically upon the carrier injection conditions and Monte Carlo simulations show that this dependence results from the variation in the degree of noisy feedback processes on the position of the injected carriers.