SIMULATION OF DEEP AND SHALLOW TRAPS IN TYPICAL PN JUNCTION SOLAR CELL USING IMPEDANCE SPECTROSCOPY

摘要

Impedance Spectroscopy measures the dielectric properties of a device as a function of frequency. Impedance spectroscopy is known to be a very convenient experimental technique for analyzing majority carrier traps. Using temperature depended impedance spectroscopy in a broad frequency range (5 Hz - 13 MHz), we have found that the AC behavior of typical pn junction diode exhibits several features. The frequency-dependent impedance data of typical pn junction has been discussed on the basis of a discrete deep or shallow trap model. The analytic results show that frequency depended -dC/dω and tanΦ curves are peaks function. The peak position is related to the deep or shallow trap states. The dielectric relaxation time and trap energy corresponding to peak frequency can be determined by -dC/dω vs ω or tan δ vs ω curve. This investigation shows that the existence of traps can be deduced from suitable complex impedance measurement and this information can be used to calculate the dielectric relaxation time and energetic position of the trap. A theoretical analysis and computer simulation are presented in order to illustrate the nature of the trap and the technique by which accurate dielectric relaxation time and energy position of the trap state can be obtained.