Detection of Nonradiative Recombination Centers in GaPN (N:0.105 %) by Below-Gap Excitation Light without Temperature Effect

Abstract

Utilization of cascade photo-excitation via intermediate band (IB) is promising for improving efficiency of IB-type solar cells (IBSCs). As Nitrogen (N) in GaP introduces defect levels as well as forming the IB, it is indispensable to detect and eliminate such defects acting as nonradiative recombination (NRR) centers during growth process. In continuation of detecting NRR centers in $\mathrm{GaPl}-\mathrm{xNx} (\mathrm{x} > 0.5 \%)$ , we studied lower N concentration region by adding a below-gap excitation (BGE) light and observing the intensity change of photoluminescence (PL). Detection in low N region of GaP1-xNx is difficult but important for understanding the initial formation and properties of defects. Elimination of temperature quenching by immersing the sample into liquid nitrogen revealed us a presence of NRR centers also in $\mathrm{GaP}_{1-\mathrm{x}}\mathrm{N}_{\mathrm{x}}(\mathrm{x}=0.105 \%)$ . Deeper understanding of IB and defects leads us a proper optimization of IBSCs.