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A theoretical method for calculating the electron mobility in quantum dot infrared photodetectors is developed. The mobility calculation is based on a time-dependent, finite-difference solution of the Boltzmann transport equation in a bulk semiconductor material with randomly positioned conical quantum dots. The quantum dots act as scatterers of current carriers (conduction-band electrons in our case), resulting in limiting their mobility. In fact, carrier scattering by quantum dots is typically the dominant factor in determining the mobility in the active region of the quantum dot device. The calculated values of the mobility are used in a recently developed generalized drift-diffusion model for the dark current of the device [Ameen et al., J. Appl. Phys. 115, 063703 (2014)] in order to fix the overall current scale. The results of the model are verified by comparing the predicted dark current characteristics to those experimentally measured and reported for actual InAs/GaAs quantum dot infrared photodetectors. Finally, the effect of the several relevant device parameters, including the operating temperature and the quantum dot average density, is studied.

Resonant cavity enhanced photodetectors (RCE-PDs) are promising candidates for applications in high-speed optical communications and interconnections. In these high-speed photodetectors, both high bandwidth and high external quantum efficiency can be achieved simultaneously because of the multipaths of the incident light due to the presence of the FabryPérot cavity into which the photodetector is inserted. In this paper, state-of-the-art RCE-PDs are discussed. Different structures of the RCE-PDs such as RCE-PIN, RCE-APD, and RCE-MSM PDs are presented and discussed. The material requirements for the RCE PDs with different material system compositions for the different structures and different wavelengths of the incident light that the photodetectors are sensitive to, are discussed. An overview of the analysis and a SPICE model of the RCE-PDs will be presented. These analyses include the calculations of quantum efficiency (QE), impulse response and frequency response of RCE-PDs. These analyses are sensitive to the standing wave effect (SWE) and to carrier diffusion, and both effects are studied. Optimization procedures for the design of ultrafast RCE-PDs will be presented, showing how the QE, bandwidth and speed of these photodetectors can be improved by adjusting the parameters of both the cavity and the photodetector itself. Finally, comparisons to experimental results and a survey of the performance of state-ofthe-art of RCE-PDs will be presented.