Direct Observation of Self-Heating in III–V Gate-All-Around Nanowire MOSFETs

Gate-all-around (GAA) MOSFETs use multiple nanowires (NWs) to achieve target ION, along with excellent 3-D electrostatic control of the channel. Although the self-heating effect has been a persistent concern, the existing characterization methods, based on indirect measure of mobility and specialized test structures, do not offer adequate spatiotemporal resolution. In this paper, we develop an ultrafast high-resolution thermoreflectance (TR) imaging technique to: 1) directly observe the increase in local surface temperature of the GAA-FET with different number of NWs; 2) characterize/interpret the time constants of heating and cooling through high-resolution transient measurements; 3) identify critical paths for heat dissipation; and 4) detect in situ time-dependent breakdown of individual NW. Combined with the complementary approaches that probe the internal temperature of the NWs, the TR-images offer a high-resolution map of self-heating in the surround-gate devices with unprecedented precision, necessary for the validation of electrothermal models and the optimization of devices and circuits. In addition, we develop the simple compact model of the complex structure, which can explain experimental observations and can provide the internal temperature of the NWs.