Photothermal response of a micropolar semiconductor medium with variable thermal conductivity: A memory-dependent nonlocal dual-phase-lag approach

Modern micro- and nanoscale semiconductor devices and MEMS often operate under intense thermal and optical loading. Classical heat transfer and elasticity theories frequently fail to predict their reliability accurately because they overlook finite memory, spatial nonlocality, and microstructural rotations. To address these limitations, this study develops a unified analytical framework for the coupled thermomechanical and photothermal response of a micropolar semiconductor medium. Four interacting mechanisms are incorporated: memory-dependent (MD) nonlocal heat conduction, temperature-dependent (TD) thermal properties, photothermal carrier transport, and micropolar coupling. The thermal conductivity is treated as a genuine function of the evolving temperature field, and the Kirchhoff transformation is applied to the full nonlinear operator before linearization is introduced in the coupling terms. The main contributions are threefold: a memory-dependent derivative (MDD) with a polynomial kernel that captures finite-window effects without the computational complexity of fractional calculus; application of the Kirchhoff transformation to handle the nonlinearity of TD properties; and derivation of closed-form analytical solutions via joint Laplace–Fourier transformations. The results show that a negative temperature-dependent conductivity coefficient causes pronounced heat and stress trapping near the irradiated boundary, increasing the risk of surface degradation. In contrast, spatial nonlocality smooths temperature gradients there but amplifies subsurface stresses and displacements. The memory parameters act as temporal averaging mechanisms, reducing peak temperatures while promoting deeper heat penetration. These insights provide quantitative benchmarks for optimizing the design, thermal management, and reliability assessment of advanced microelectronic and optoelectronic systems.