Breaking the material-limited temperature coefficient of resistance via carrier feedback in a single transistor

The temperature coefficient of resistance (TCR) is one of the most fundamental properties of a material. Semiconductor materials exhibiting high TCR are promising candidates for applications in high-resolution thermal imaging for autonomous systems, high-precision temperature sensing, and neuromorphic computing. However, the TCR magnitude is typically below 5%/K near 300 K for thermal imaging materials, such as vanadium oxide and amorphous silicon. Inspired by the distinctive characteristic of feedback in electronic circuits, we demonstrate a voltage-tunable TCR of up to 150%/K near 300 K in a two-terminal InGaAs/InP n-p-n transistor, enabled by an internal coherent carrier feedback mechanism. In this device, current amplification arises from a synergistic interplay between temperature-dependent transistor gain and avalanche multiplication. Carriers amplified at the emitter-base junction via the transistor effect are injected into the collector-base junction, where avalanche multiplication generates additional carriers. These excess carriers are then fed back to the emitter-base junction, triggering further transistor amplification. This regenerative positive feedback loop results in a high and bias-tunable temperature coefficient of resistance (TCR). This work reveals the potential of device engineering in overcoming the fundamental material-level physical limits of temperature properties.