Simulation of Inorganic/Organic Hybrid Vertical Light-Emitting Transistors: Unraveling the Roles of Heterojunction Barrier, Carrier Mobility, and Source Design in Realizing High-Efficiency, Uniform Emission

Vertical light-emitting transistors (VLETs) are emerging as promising candidates for next-generation display technologies, offering advantages such as low operating voltages, rapid switching, and high-aperture-ratio surface emission. Among them, inorganic/organic hybrid VLETs uniquely integrate the excellent electrical properties of inorganic semiconductors with the tunable optical functionalities of organic emitters. Despite their potential, the underlying mechanisms governing charge transport and electroluminescence (EL) in these hybrid architectures remain insufficiently understood. In this study, we present a comprehensive simulation-based investigation of hybrid VLETs featuring an encapsulated source design with zinc oxide (ZnO) as the electron transport channel and Super Yellow (SY) as the emissive polymer. Using Technology Computer-Aided Design simulations calibrated with experimental data from ZnO transistors and SY single-carrier diodes, we develop a predictive model that captures the fundamental processes of charge injection, transport, and recombination in the ZnO/SY VLET, alongside a reference organic light-emitting diode (OLED) for benchmarking. The simulations reveal the formation of a recombination zone localized at the ZnO/SY heterojunction with a large effective channel depth (deff) on the order of 103–104 μm, which supports spatially uniform EL over extended areas. This depth decreases with increasing drain bias, consistent with the field-dependent EL observed experimentally. Parametric analyses further elucidate the primary importance of minimizing the ZnO/SY interface injection barrier and maximizing electron mobility in ZnO to achieve high-efficiency and large-area emission. A pronounced mobility contrast between ZnO and SY also promotes lateral current spreading, effectively extending deff and enhancing emission uniformity. Furthermore, geometric optimization of dual-stripe source configurations demonstrates that reducing the aperture width below deff to approximately 100 μm significantly improves both the current output and uniformity, approaching the OLED-level performance while maintaining a high aperture ratio (∼90%). This improvement is attributed to electrostatic flattening of lateral potential gradients, thereby producing a uniform vertical bias across the active layers similar to OLED operation. Overall, this work elucidates the physical operating principles of hybrid VLETs and provides concrete design guidelines for advancing their efficiency, scalability, and integration in future optoelectronic and display applications.