Evidence of the Meyer-Neldel Rule in InGaAsN Alloys: Consequences for Photovoltaic Materials

We present data showing the potential adverse effects on photovoltaic device performance of all traps in InGaAsN. Deep-level transient spectroscopy measurements were performed on InGaAsN samples grown by both metal-organic chemical vapor deposition and RF plasma-assisted molecular-beam epitaxy. For each growth technique, we studied samples with varying nitrogen composition ranging from 0% to 2.2%. A deep hole trap with activation energy ranging between 0.5 and 0.8 eV is observed in all samples. These data clearly obey the Meyer-Neldel rule, which states that all traps have the same emission rate at the isokinetic temperature. A fit of our trap data gives an isokinetic temperature of 350 K, which means that both deep and shallow traps emit slowly at the operating temperature of solar cells-thus, the traps can be recombination centers.