Abstract: This study investigates the radiation response of silicon-based <111> NPN bipolar junction transistors (BJTs) (2N6688) under irradiation with 110 MeV Si⁸⁺ heavy ions for applications in space and radiation-rich environments. The devices, produced by Bharath Electronics Limited (BEL), were irradiated at the Tandem accelerator facility at the Inter University Accelerator Centre, New Delhi. Fluences ranged from 5×109 to 1×1013 ions/cm², with the beam current maintained at 1 pnA to minimize thermal effects during irradiation. Simulations using SRIM and TRIM showed a projected ion range of 39.62 µm, with energy deposition predominantly due to electronic energy loss (LET = 10.2177 MeV/(mg/cm²)). Experimental results revealed a significant increase in base current (IB) with radiation fluence, as characterized at different temperatures (27°C, 50°C, and 100°C). At a fluence of 1×1012 ions/cm², IB increased from 48.66 µA (unirradiated) to 1165.66 µA at 27°C, from 147 µA to 1755 µA at 50°C, and from 317.66 µA to 1885.33 µA at 100°C. These trends indicate a monotonic increase in IB with fluence and temperature, suggesting a combination of total ionizing dose (TID) effects and displacement damage (NIEL) as key contributors to device degradation. The findings highlight the sensitivity of BJTs to radiation, emphasizing the importance of understanding radiation-induced degradation mechanisms for the design of robust devices in high-radiation environments