Carrier Screening and Potential-Difference Response of a Piezomagnetic–Piezoelectric Semiconductor PN-Junction Sandwich Fiber Under a Local Magnetic Field

Carrier screening and observation geometry determine how a local magnetoelectric response contributes to a potential-difference readout. This study develops a finite-length one-dimensional analytical model for a weak PN-junction piezoelectric-semiconductor fiber between magnetostrictive layers subjected to a localized magnetic-field increment about a prescribed bias. Cross-sectional force balance, two-carrier drift–diffusion, blocking end conditions, and interface continuity yield a four-region solution that separates the junction reference from the magnetic increment. In the representative weak-junction case, the end-to-end difference is about 1% of the peak local magnetically induced potential, whereas observation pairs at the field-region edges and near the junction give differences about 200 and 50 times larger than the end-to-end value. For equal screening and a step field, the response of a fixed interior pair peaks when the field-region edges reach the observation points. Uniformly doped and symmetric weak-junction controls have identical magnetic increments under equal screening despite their different reference fields. Layer thickness modifies both magnetic conversion and carrier screening. The resulting continuum-model relations identify how excitation width, screening length, and observation position jointly govern internal magnetic-field readout.