Direct recognition of non-radiative recombination centers in semi-insulating LEC InP:Fe using double excitation photoluminescence

In order to observe the effect of intra-band gap excitation on the photoluminescence (PL) properties of undoped InP and iron doped InP (InP:Fe), PL measurements were performed in InP crystals with thickness of 360 μm and area of about 4×3 mm2, grown by the liquid encapsulated Czochralski (LEC) technique upon excitation with both Ar-ion laser and 980 nm light. The PL intensities for InP:Fe under 980 nm wavelength light illumination relative to no illumination increased by about 52%, 33%, and 12% for the 1.337, 1.380, and 1.416 eV peaks, respectively, at 10 K, whereas there was no illumination effect for undoped InP. This is a strong indication that Fe centers play a role as non-radiative recombination centers to decrease the PL intensity. PL experiments were performed in the spectral range of 1320-1440 meV for InP in the sample temperature range of 10-160 K. The electron and hole photoionization cross-sections at 980 nm wavelength light illumination were calculated as σn0[Fe2+/3+→CB]=2.34×10-18cm-2 and σpo[VB→Fe2+/3+]=8.20×10-17cm2, respectively.