Quantitative heterodyne lock-in carrierographic imaging of silicon wafers and solar cells

InGaAs camera-based high-frequency heterodyne lock-in carrierographic (LIC) imaging of Si wafers and solar cells is introduced. The nonlinearity exponents of the photocarrier radiometric signals of the samples were measured by intensity scan. Heterodyne LIC images in a wide frequency range (0.1 - 20 kHz) were obtained and the amplitude-frequency behavior was quantitatively analyzed. A contrast inversion phenomenon was observed in high frequency images which highlights image contrast from defective regions against a fading background. High frequency LIC imaging results in high-resolution and near-subsurface information, thus having excellent prospects for fundamental research and industrial in-line non-destructive testing of photovoltaic materials and devices.