We present the results of a new analytical model for the analysis of the dark current in realistic quantum dot infrared photodetectors (QDIPs). This model includes the effect of the space charge formed by electrons captured in QDs and donors, the self-consistent electric potential in the QDIP active region, the activation character of the electron capture and its limitation by the Pauli principle, the thermionic electron emission from QDs and thermionic injection of electrons from the emitter contact into the QDIP active region, and the existence of the punctures between QDs. The developed model yields the dark current as a function of the QDIP structural parameters, applied voltage, and temperature. It explains some features of the dark current characteristics observed experimentally.

We study the effect of acoustic-phonon confinement on the energy and momentum relaxation of a twodimensional electron gas in thin films. The interaction via the deformation and piezoelectric potentials with a complete set of phonon modes in films with stress-free and rigid surfaces is taken into account. We demonstrate that in thin films the modification of the phonon properties and screening brings about substantial changes of the electron relaxation rates in comparison to the case of interaction with bulk phonons at low temperatures, where the effective reduction of the phonon spectrum dimensionality takes place. For suspended films, relaxation rates are substantially enhanced: the temperature dependence of the momentum and energy relaxation rates, in films with nonmetallized ͑metallized͒ surfaces, is found to be T 7/2 (T 5/2) for both deformation potential and piezoelectric mechanisms. The reason for such an enhancement is the strong scattering of electrons by flexural phonons having quadratic dispersion and a high density of states at low frequencies. Conversely, for films with rigid surfaces the low-temperature relaxation of electrons is exponentially suppressed due to the formation of a gap in the phonon spectrum.

We propose a device model for quantum dot infrared photodetectors (QDIPs) with relatively large lateral spacing between QDs as occurs in QDIPs fabricated and experimentally investigated recently. The developed model accounts for the self-consistent potential distribution and features of the electron capture and transport in realistic QDIPs in dark conditions. The model is used for the calculation of the dark current as a function of the structural parameters, applied voltage and temperature. It explains a rather sharp increase in the dark current with increasing applied voltage and its strong sensitivity to the density of QDs and the doping level of the active region. The calculated dependences are in good agreement with available experimental data. The obtained characteristics of QDIPs are compared to those of QWIPs with similar parameters.

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