As foreseen by Keyes in the late 1960s, the self-heating effect has emerged as an important concern for device performance, output power density, run-time variability, and reliability of modern field-effect transistors. The self-heating effect is aggravated as the device footprint scales down for higher level of integration (low-power devices) or as the devices are operated in ultrahigh voltage regimes (high-power devices). In this article, we focus on the implications of self-heating on hot carrier degradation (HCD) of modern transistors by integrating within a coherent theoretical framework a broad range of experimental data scattered in the literature. We explain why system integration exacerbates transistor self-heating, while high-frequency digital operation ameliorates it, suggesting an opportunity for co-optimization. We conclude this article by discussing the various material-device-system design strategies to reduce HCD and suggesting open problems for further research.

Stretchable electronics represent a new generation of electronics that utilize soft, deformable elastomers as the substrate or matrix instead of the traditional rigid printed circuit boards. As the most essential component of stretchable electronics, the conductors should meet the requirements for both high conductivity and the capability to maintain conductive under large deformations such as bending, twisting, stretching, and compressing. This review summarizes recent progresses in various aspects of this fascinating and challenging area, including materials for supporting elastomers and electrical conductors, unique designs and stretching mechanics, and the subtractive and additive patterning techniques. The applications are discussed along with functional devices based on these conductors. Finally, the review is concluded with the current limitations, challenges, and future directions of stretchable conductors.