Thermoelectric power on p-n junction

The measurements of thermo-emf were performed on sharp PbTe p-n junctions with doping layer depth by order of diffusion length of minority carriers an the temperature range from 300 to 80 K. The barrier thermo-emf Vb effect results in sharp output signal increase at low temperature. Moreover, at sign of Vb is opposite the sign of volume thermo-emf. The barrier thermo-emf may be explained thermodiffusion nonequalibrium carriers and its separation on p-n junction. However the difference Vb from photo-emf is opposite sign of its terms at n- and p-ranges. At our case the observation of Vb became enabled by the producing ΔT only at n-range (the absorption of short laser pulse on free carriers at surface layer). At short pulse (CO₂-laser λ = 10.6 μm, τ = 200 nsec) increase of output signal practically repeated the form of laser pulse, i.e. irradiation absorption of free carriers and its interation with lattice (heat of phonon system) is acting without inertion. At same time we observed very slow decreasing in signal V (μsec and more) after switch off, connecting with inertion of phonon system cooling. This memory effect of V differs from response of photo-emf and may be very useful for concrete applications (for example measurement of power for short laser pulse).