Analysis of the induced photothermal conduction in the Mn4Si7-Si〈Mn〉-Mn4Si7 and Mn4Si7-Si〈Mn〉-M heterojunctions

The kinetics of photocurrent is studied in the presence of the intrinsic irradiation at hν ≥ 1.12 eV in the Mn4Si7-Si〈Mn〉-Mn4Si7 and Mn4Si7-Si〈Mn〉-M heterojunctions at relatively high applied voltages. It is demonstrated that photocurrent, scattered power, and temperature at the reverse-biased contact of the heterojunction depend on time at dc applied voltage, low temperature, and irradiation at hν ≥ 1.12 eV. The analysis of the temperature dependences of the photocurrent growth with time is used to demonstrate that the photocurrent pulses consist of two fragments: the first one corresponds to a slowly increasing relatively low current with a slope of (2–4) × 10−4 A/s and the second fragment is characterized by a sharp increase in the current with a slope of 0.1–1.0 A/s. Based on the slopes, the heating rates (β1 = 42 deg/s and β2 = 3 × 103 deg/s) and temperature gradients across the transient layer that corresponds to the Mn4Si7-Si〈Mn〉 interface (ΔT/Δx = 6.3 × 106 K/cm for β1 = 42 deg/s and ΔT/Δx ≥ 1.5 × 108 K/cm for β2 = 3 × 103 deg/s) are estimated. It is demonstrated that the Joule self-heating allows relatively high heating rates in the reverse-biased contact of heterojunction, which provides rapid heating similar to the rectangular step excitation that is equivalent to the activation of the long-wavelength (extrinsic) irradiation.