Investigating Defect-Assisted Emission in BaSi2 by Power Dependent Photoluminescence

Undoped bulk BaSi
2
on Si(111) substrate was studied by power dependent photoluminescence (PL). The Ba-to-Si deposition rate ratio of the sample is 3.7. At 10 K, PL spectrum consists of multiple peaks with energies smaller than the band gap. As the excitation power is increased, the low energy peaks become saturated while the high energy peaks become more pronounced. The PL spectrum was best fit with four Gaussian curves with PL peak energies of 1.12, 1.05, 0.992 and 0.878 eV. The power law exponents obtained from the experiment is then compared with the calculated exponents based on the rate equations. It was found that four defect levels may be present in the sample which are shallow donor, shallow acceptor, deep donor, and deep acceptor. The concentration of deep donor and deep acceptor (which responsible for the 0.878 eV PL peak) is relatively low and easily saturated at low excitation. However, the concentration of shallow acceptor is relatively high, remain unsaturated at high excitation and is attributed to the Ba antisite defect.