Balancing Injection and Short‐Channel Effects in Organic Permeable Base Transistors via Thickness Scaling

Organic permeable base transistors (OPBTs) have attracted attention as vertical organic transistors that achieve high current density at a low operating voltage. While reducing organic semiconductor thicknesses is a common approach to improve performance in OPBTs, its subtle influence on contact resistance and carrier transport remains unclear. Two‐dimensional finite‐element simulations and experiments show the separate roles of the top and bottom organic semiconductors and quantify their thickness‐dependent impacts on transport during device scaling. It turns out the top organic semiconductor is coupled to the injection barrier height. At low injection barriers, decreasing the top thickness lowers the contact resistance and enhances device performance. Excessively thinning the top organic semiconductor, however, limits carrier spreading along the interface and degrades device performance because, under higher injection barriers, lateral expansion of the effective injection area is required for efficient carrier transport. In the case of the bottom organic semiconductor, short‐channel effects mainly matter. As the bottom thickness decreases, the collector potential lowers the base energy barrier, triggering short‐channel effects. Concurrent reduction strengthens both injection‐related limitations and short‐channel effects, causing overall performance degradation. These findings support that balanced engineering of the top and bottom organic semiconductors is required to realize high‐performance OPBTs.