The thermoelectric power on p-n junction

Abstract

Measurements of thermo-EMF were performed on sharp PbTe p-n junctions with doping layer depth by order of diffusion length of minority carriers in the temperature range from 300 to 80 K. The barrier thermo-EMF Vb effect results in sharp output signal increase at low temperature. Moreover, the sign of Vb is opposite to the sign of volume thermo-EMF. The barrier thermo-EMF may be explained by thermodiffusion nonequilibrium carriers and its separation on the p-n junction. However the difference Vb from photo-EMF is an opposite sign at n- and p-ranges. In this case the observation of Vb was enabled by producing /spl Delta/T only at n-range (the absorption of short laser pulse and free carriers at surface layer). At short pulse (CO/sub 2/-laser /spl lambda/=10.6 /spl mu/m, /spl tau/=200 nsec) increase of output signal practically repeated the form of the laser pulse, i.e., irradiation absorption of free carriers and its interaction with lattice (heat of phonon system) is acting without inertion. At the same time we observed very slow decrease in signal V (/spl mu/sec and more) after switch off connecting with inertion of phonon system cooling. This memory effect of V differs from the response of photo-EMF and may be very useful for concrete applications (for example measurement of power for short laser pulse).