We demonstrate a systematic way to understand and select the accelerating voltage for maximizing cathodoluminescence (CL) by correlating the carrier diffusion length with the efficiency of ultraviolet (UV) InGaN/AlGaN multiple quantum wells (MQWs). We showed that the absorption of MQWs benefits from the absorbed energy within the diffusion length below the MQWs. With this understanding, we have achieved good agreement between the experimental data of and the Monte Carlo (CASINO) simulations on the dependence of acceleration voltage and QW number on InGaN/AlGaN MQW structures. These findings indicate that CL-based UV generation from carefully engineered III-N MQW structures with an appropriate number of QWs is highly promising. The understanding and application of this work can be extended to electron-beam pumped devices emitting in deep-UV (200-280 nm) wavelengths. © 2022 Author(s).