Spike-notch structure of (AlGa)As heterojunctions

The I-V characteristics and optical properties of (AlGa)- As p-n heterojunctions, with a larger bandgap on the n side, were studied. The discontinuity of conduction bands, tilted by the space-charge electric field, produces a spike-notch structure. At comparable low doping levels on both sides of the heterojunction, the notch is empty at zero-bias conditions and acts as a trap for injected electrons. Thermal injection into the p-type region becomes the predominant current mechanism after the notch has been filled with electrons. The notch population is a step function of the applied voltage and determines an S-shaped I-V characteristic. Radiative recombination and ac photocurrent under dc bias gives further support for the existance of captured electrons in the notch.