Influence of Polarization on the Efficiency of InxGa1-xN/GaN p–i–n Solar Cells

Abstract

The net polarization charge and induced internal electric field can positively or negatively affect the performance of InGaN-based optoelectronic devices, depending on the formation of the polarization charge. While positive polarization charges at the InGaN/n-GaN interface are supposed to affect solar efficiency positively by increasing the electric field, negative polarization charges at the InGaN/n-GaN interface negatively affect efficiency by forming an energy barrier. However, the solar performance is not improved in a beneficial case when the polarization charge reaches 1020 cm-3. In the detrimental case, the efficiency of p-GaN/i-In0.1Ga0.9N/n-GaN solar cells is seriously degraded from 2.75 to 0.49% as the polarization charge increases from 0 to 2.5×1018 cm-3. The insertion of graded layers with a slowly increasing In content is proposed to relax the polarization, and shown to improve solar efficiency.