Abstract:
The noise spectra was measured and analyzed, of a heterojunction structures, with a GaAs emitter sandwiched between two AlGaAs barriers. One of the barriers here was slanted (graded) by gradually changing the aluminum fraction, whilst the second barrier was kept flat (constant). A structure, with both barriers are flat, was used as the control sample. Results show the presence of different noise components such as the generation–recombination (G-R), 1/f, Johnson, and Shot noise in both devices. Taken as total and as individual components, the lowest noise spectra were observed for the flat barrier device. The high noise in the graded barrier device is attributed to the high dark current resulted by low internal resistance in the structure and the two G-R noise sources were identified as the deep traps (at ~0.54 eV and ~0.39 eV above the valence band of AlGaAs) possibly resulted by do pant migration and defects.
