Effect of heterojunction spike on the quantum efficiency of an AlGaAs/GaAs heterojunction charge coupled device

The ’’spike’’ in the conduction resulting from the band-gap discontinuity in a p- GaAs/n-Al0.3Ga0.7As heterojunction is observed via the blocking of photoexcited electron flow from the p-GaAs to the n-Al0.3Ga0.7As. The spike height deduced from photocurrent versus bias results is 0.14 eV above the conduction-band minimum of p-GaAs. This value is 0.13 eV lower than that predicted by theory and suggests a positive interface charge density of 4×1011 cm−2. The lowered barrier does not appear to reduce the electron collection in the charge coupled device operation under low light level illumination.