The III-nitride material system offers substantial potential to develop high-efficiency solar cells. The solar cell operation requires the formation of a depletion region. Conventionally, this is achieved by a p-n junction. The piezoelectric polarization introduces a strong band bending at the hetero-junction interface and hence creating a depletion region. The growth of a thin AlN or GaN epi-layer on InGaN introduces the required piezoelectric polarization to create a depletion region. This paper presents the polarization-incorporated simulations in "Silense" showing the depletion region formation by GaN or AlN epilayers on p-InGaN. Three structures are then MOCVD grown and characterized for crystal quality and electrical properties. The fabricated devices demonstrated the diode characteristics with an open-circuit voltages > 2.0 V.