Fermi Level Control and Thermal Current Densities in Selectively Doped P-I-N Multiquantum Well Photovoltaic Structures, Under Illumination

III-V semiconductor multiquantum-well (mqw) photovoltaic devices show improved collection and transport properties when they are selectively doped. Existence of multiple quantum wells is of advantage because of (a) easier carrier collection (b) photocarrier separation (electrons vs holes) that reduces recombination and (c) of Fermi level shifting. The latter is of real advantage when the Fermi level is forced to be pinned within a quantum well, especially in the vicinity of the two sub-bands. Studying of the latter pinning is typically done via the neutrality equation. Charge neutrality condition is taken into account and includes (I) carriers contributed to quantum wells by shallow donor impurities embedded in the neighboring wide gap material (II) carriers contributed to the conduction band continuum (III) trapped carriers in the quantum wells, under dark conditions (IV) doping concentration levels and (V) layer widths. Under illumination, excess carriers are generated in the quantum wells, which thermally escape to the conduction continuum. Thermal currents are predicted to maximize at low temperatures, while significant current contribution is succeeded at high temperatures as well. Key-Words: Fermi level, Quantum wells, photovoltaic heterostructures