Analysis and Simulation of Superlattice GaN/InGaN p-i-n Solar Cells

Abstract

Indium gallium nitride (InGaN) is becoming a promising semiconductor material for fabrication of solar cells due to its high absorption coefficient (about 10⁵ cm⁻¹) and tunable (by its In content) direct band-gap, from 0.71 eV (E_InN) to 3.43 eV (E_GaN). Solar cells based on structures with variable In content should show a reduction of thermalization losses, absorbing almost the whole of solar spectrum. Unfortunately, these advantages are partially lost and InGaN solar cells performance reduced due to technological issues (low quality of InGaN layer growth on GaN substrate) and wurtzite nature of InGaN semiconductor (spontaneous and piezoelectric polarizations), in particular in case of In-rich ternary alloy. This paper is focused on the parametric analysis and simulation of an intermediate band (IB) superlattice GaN/InGaN p-i-n solar cell on GaN quasi-bulk substrate. Photovoltaic device performances are investigated and simulated as a function of both In concentration in GaN/InGaN quantum wells (QWs) and QW number. For a superlattice with 28 QWs, an efficiency of 1.05 % with a short-circuit current density of 1.193 mA/cm² has been achieved. Furthermore, some considerations on the possibility to obtain a more efficient InGaN solar cell with a wider absorption spectrum using InN quantum dots (QDs) in a photovoltaic device structure are also derived.