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Admittance spectroscopy of GaInNAsSb-based solar cell structure, where thermally active defects were determined in the i-GaInNAsSb layer of the structure. (a) temperature dependent steady state capacitance, C, measured with AC modulation voltage in the frequency range between 1 KHz–1 MHz. Capacitance steps in the figure correspond to the defects D1 and D2 in the i-GaInNAsSb layer. Inset of figure shows the Arrhenius plot of the D1 and D2. (b) Defect density spectrum of the i-GaInNAsSb film in the structure. Solid line (red) is the Gaussian fitting of the defect band. Trap concentration was calculated from the area under the fitting curve.
(a) RT PR spectrum of the GaInNAsSb-based solar cell structure, and (b) spectral dependence of the TPC spectrum of the similar structure measured at RT, where optical levels were identified in i-GaInNAsSb layer of the structure. Solid symbols (wine color) in the figure represent negative TPC signal (absolute value), which corresponds to OH1-defect (will be discussed in Fig. 3 ).
TPC signal of the GaInNAsSb-based solar cell structure measured at T = 105 K, where optical transitions were probed from the i-GaInNAsSb layer of the structure. Open symbols represent positive TPC signal, while negative TPC signal (absolute value) in the spectrum is marked with solid symbols (wine color). Solid line (dark yellow) is the Gaussian fitting of the defect band. Inset of figure shows schematic diagram of various sub-band-gap optical transitions in the i-GaInNAsSb film.
Summary of the thermally active trap centers in the i-GaInNAsSb film determined by admittance spectroscopy. Experimental values of the thermal activation energy (E A), thermal capture cross section (σ t), and trap concentration (N t) of each defect are shown in table.
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