Explicit Derivation of Dark Thermionic Current Densities in III-V Multiquantum Well Infrared Photodetectors

We propose an analytic calculation of the dark current density for GaAs/A1GaAs thick barrier quantum well infrared photo-detectors (QWIP's). We evaluate the dark current component, by integrating (a) drift velocity of the carriers via their kinetic energy (b) the non-tunneling probability factor 1-T (E) (c) the Fermi factor and (d) the 3-d density of states (DOS) of the multiple quantum well structure. We find that the dark currents depend on the temperature T, applied bias Vb, aluminum molar ratio (and hence barrier height )), cut-off energy )E=Ec-EF and peak wavelength according Incorporation of superlattices in infrared photodetectors leads to a T term, which is due to the 2-dimensional electronic gas (2DEG) of the wells. We find that dark thermionic current densities (a) increase dramatically with temperature under fixed bias levels (42 mA/cm at 80°K & 30 mV and 1.512 A/cm at 100°K & 30mV) (b) increase with applied voltage at fixed temperatures (e.g. 0.0018 A/cm to 0.7445 A/cm at 80°K, from 10mV to 50mV), both at peak wavelengths of 10μm.