Comprehensive study of interface state via the time-dependent second harmonic generation

Electric field induced time-dependent second harmonic generation (TD-SHG) is an emerging sensitive and non-contact method for qualitatively/quantitatively probing semiconductor parameters. The TD-SHG signal is related to the evolution of the built-in electric field due to laser-induced electron generation and transportation. Here, we conducted a comprehensive study of fixed charge density (Qox) and interface state density (Dit) using the conventional conductance method to compare them with the SHG signal from TD-SHG. The extracted Qox is around 2.49 × 1010 cm−2 regardless of SiO2 thickness, corresponding to the constant SHG intensity at the minimum of TD-SHG. The extracted Dit linearly decreases with the SiO2 thickness, which is related to the linear change of extracted time constant from TD-SHG. Therefore, the TD-SHG, being a sensitive and non-contact method as well as simple and fast, can serve as an alternative approach to test the semiconductor parameters, which may facilitate semiconductor testing.