Deformation of a deep-level transient spectroscopy spectrum by an inhomogeneous carrier concentration depth profile

Abstract

Numerical calculation of a deep-level transient spectroscopy (DLTS) spectrum was carried out for δ-doped samples. Inhomogeneous carrier distributions are assumed with two types, which were based on Gaussian and Lorentzian functions. The simulated DLTS spectra are deformed when the depletion region edge passes the carrier inhomogeneous region. The DLTS spectrum narrows when its peak shifts to a higher temperature, and becomes broader when it shifts to a lower temperature. Deformed DLTS spectra offer incorrect information of trap parameters. An intensive waveform analysis would mislead to an existence of some traps even if only one trap exists. Dependences of the spectrum on the values of the time constant and the reverse bias in DLTS measurements are valid to evaluate whether the spectrum is deformed by the carrier inhomogeneous distribution. In practical DLTS measurements, much attention should be paid for samples whose carrier distribution changes abruptly in depth.