Quantum structure Infrared Photoetectors (QsIPs) are based on Intersubband transitions. GaAs mature technology makes Quantum Well Infrared Photodetectors (QWIPs) very attractive for their flexibility to enhanced device functionality and ease of integration with optoelectronic devices. Quantum Dot Infrared Photodetectors (QDIPs), based on 3-D confinement, are an evolution of QWIPs. They are expected to achieve higher detectivities. Charge transport has been investigated by current noise analysis, on QWIPs and QDIPs. Peculiar dynamics, beyond the expectations of noise models in literature, have been evidenced experimentally in QWIPs. An analytical model, based on a Langevin approach, has been developed and qualitatively reproduced real noise spectra. QDIP high performances have been hampered, so far, by homogeneity lack in self-assemble growing technology. Photoresponsivity and Noise spectra were found closely related to quantum dot inhomogeneity. Further insights has been added in the complex new phenomena observed in QDIPs. This work should help specialists as well anyone else who may be interested in better understanding the complex physics of QsIPs and the investigation methods.