Observation of a soret-dufour effect for laser-generated carriers in germanium

The absorption of high-intensity laser radiation in semiconductors can generate high carrier densities and temperatures. If the absorption coefficient is high, large lattice temperature gradients and, therefore, band-gap gradients are produced. Under certain conditions it is possible for temperature gradients and not density gradients to dominate the carrier diffusion process, with carrier confinement near the surface being possible. We present preliminary evidence of this effect based on 10.6 μm reflectivity probing of carriers generated by 0.53 and 1.06 μm excitation pulses in germanium.