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In this letter, the photovoltaic characteristics of InGaN/AlGaN superlattice solar cells with In=21% and 40% in InGaN multiple quantum wells, and Al=14% and 20% in AlGaN barriers are investigated. The results obtained numerically show that an increment of 18.2% in short-circuit current density is achieved by introducing p-type doped (holenconcentration = 3×1017 cm-3) Al0.2Ga0.8N barriers in In0.4Ga0.6N superlattice solar cell when compared with undoped Al0.14Ga0.86N barriers. This improvement is mainly attributed to the increased electric field in the main absorption region, which is beneficial for the holes in the valence band to move towards the p-region. The capability of carrier transport is efficiently improved, thus increasing the carrier-collection efficiency and the conversion efficiency.

The influence of spontaneous and strain-induced piezoelectric polarizations on the photovoltaic characteristics of an Al0.14Ga0.86N/In0.21Ga0.79N superlattice (SL) solar cell is numerically investigated. The simulation results show that, compared with the conventional p-i-n structure, the Al0.14Ga0.86N/In0.21Ga0.79N SL solar cell has better photovoltaic characteristics and is less sensitive to the effect of internal polarization. Therefore, the use of an SL structure in the III-nitride solar cells is advantageous if both the polarization effect and the crystal quality are of major concern.