Electron and hole impact ionization coefficients in GaAs/Al0.45Ga0.55As/Al0.3Ga0.7As coupled well systems

Abstract

We have measured electron and hole multiplication factors and impact ionization coefficients in 550 Å GaAs/500 Å Al0.3Ga0.7As quantum wells with an intermediate Al0.45Ga0.55As barrier (50 and 100 Å) inserted in the well region. It is seen that while the measured value of α(E) is insensitive to the position of the intermediate barrier in the well, the value of β(E) is very sensitive. The value of α/β varies from less than unity to 5, depending on the position of this barrier. These results suggest that hole confinement and scattering play a major role in making the value of α/β greater than unity in these multilayered structures.