Utilizing polarization induced band bending for InGaN solar cell design

Strong polarization effects observed in 111-nitride materials can invert the surface carrier type. The corresponding band bending can be used to design InGaN solar cells. Similar surface inversion was observed in the past with silicon-based Schottky-barrier solar cells, but was limited by Fermi level pinning. The formation of two-dimensional electron gas by polarization fields in 111-nitrides has been reported. Using a similar idea, the growth of a thin AIN capping layer on p-InGaN has resulted in band bending, hence depletion region, under the surface that can be used to separate any generated photo-carriers. Hall measurements at different depths on these structures confirm the inversion of surface carrier type. Solar cells based on this concept have resulted in an open circuit voltage of 2.15 V and short circuit current of 21.8 μA.