Optical characterization of carrier recombination processes in GaPN by two-wavelength excited photoluminescence

Wave functions of N-isoelectronic levels in GaP overlap with increasing N concentration and form an intermediate band (IB) with a suitable energy allocation. Thus GaPN is a promising candidate for IB-type solar cells. Detailed characterization of defect originated recombination levels is the first step to realize the expected efficiency improvement. We have studied carrier recombination processes via the IB in GaPN with N concentration of 0.56% by two wavelength excited photoluminescence (TWEPL) measurement. Spectral behavior of high energy shoulder in the IB luminescence with increasing the density of below gap excitation (BGE) light (hv
_BGE
=1.17eV) discriminated the effect of optical excitation from that of thermal activation. The BGE effect revealed the presence of different carrier recombination levels which are connected with conduction band and with the IB, respectively.