κ-Ga ₂ O ₃ /(B)GaAs/GaAs Heterostructures: Study of Optically Active Defects, Design, and Modeling of Solar Cells Based on These Heterostructures

This work focuses on the steady-state luminescence of pure-phase κ-Ga₂O₃/GaAs and κ-Ga₂O₃/BGaAs/GaAs heterostructures grown by metal-organic chemical vapor deposition. The films were characterized by electron beam (e-beam) energy-dependent cathodoluminescence (CL) and steady-state photoluminescence (PL), supported by one-dimensional Solar Cell Capacitance Simulator (SCAPS-1D) simulation, to assess their possible application as intermediate energy band layers in solar cells. The power- and temperature-dependent PL and CL show that the luminescence in κ-Ga₂O₃/GaAs and κ-Ga₂O₃/<i>a</i>-BGaO/BGaAs/GaAs heterostructures, where <i>a</i>-BGaO represents a thin amorphous BGaO interlayer between the κ-Ga₂O₃ film and BGaAs template, is dominated by donor-acceptor transitions. These transitions originated from point defect ensembles tuned by the disorder at the interface, which give rise to the formation of minibands. The boron-to-gallium substitution, boron segregation, gallium diffusion, and point defects clustering at the interface are supposed to play a crucial role in the luminescence mechanisms. The heterojunction features are promising in view of the development of a new class of active layers in photodetectors working in the visible and infrared regions. We propose a novel solar cell structure in which the insertion of a BGaAs/<i>a</i>-BGaO interlayer between GaAs and κ-Ga₂O₃ may substantially enhance the solar cell parameters. The SCAPS-1D simulations suggest that the κ-Ga₂O₃/<i>a</i>-BGaO/BGaAs/GaAs heterostructure may reach a power conversion efficiency (PCE) of 23.76% with an open-circuit voltage (<i>V</i> _oc) of 0.92 V, a short-circuit current density (<i>J</i> _sc) of 32.61 mA/cm², and a fill factor (FF) of 78.66%.