Quantifying Joule Heating in In _<i>x</i> Ga _{1− <i>x</i>} N Structure via Polarization and Compositional Grading under External Bias

This work presents an electrothermal analysis of In x Ga 1− x N heterostructures, highlighting the influence of built‐in polarization (BIP), carrier dynamics, and compositional grading on Joule heating. The BIP field increases linearly with indium composition ( x ), reaching ≈−6.07 × 10 5 V cm −1 for x = 0.1, while –1.07 × 10 6 V −1 cm −1 for x = 0.3. Electron mobility shows dual dependence: it increases with x and decreases with higher carrier concentration due to scattering. For a doping level of 10 17 cm −3 , the mobility rises from 1228 cm 2 V −1 s −1 at x = 0.1 to 1506 cm 2 V −1 s −1 at x = 0.3. Current density is significantly modulated by BIP orientation, ranging from suppression under −BIP to enhancement under +BIP, with peak values exceeding 1 kA m −2 in 5 nm structures. Joule heating under BIP reaches ≈3.5 × 10 12 W cm −3 , which is higher than ≈2.8 × 10 12 W cm −3 for the non‐BIP structure at x = 0.2 under the same biasing conditions. Under a constant biasing condition, nonuniform heat generation occurs, leading to a spatial variation in junction temperature. These findings offer valuable design insights for optimizing thermal management in high‐power optoelectronic devices.