Minority-carrier thermoelectric devices

Traditional Peltier coolers employ majority carriers within doped semiconductor regions to transport heat energy between metal contacts. An alternative approach to using such coolers in an external fashion to cool electronic devices is to optimize the thermoelectric performance of the electronic devices themselves. Recognizing that minority carriers play an important role in many electronic and optoelectronic devices, we have developed a general theory for thermoelectric effects in a p-n diode (a prototypical electronic and optoelectronic component) where diffusion of minority carriers is essential to the device´s operation. Differences with the traditional Peltier effect are highlighted. It is also shown that the heat energy can be transported from the diode junction to the side contacts, producing temperature gradients within the device and internally cooling the junction. Analytic expressions for quantities such as the effective ZT are derived, as well as optimization conditions for doping, region width, and current density. Predicted heat gradients over micron-scale devices are approximately 7 degrees for InGaAs and 30 degrees for HgCdTe under optimal heat-sinking conditions. Other numerical results are given for several common material systems.