Experimental characterization and numerical simulation of the electrical properties of nitrogen, aluminum, and boron in 4H/6H-SiC

In order to measure the ionization time constants of dopants in 4H/6H-SiC within a wide range of temperature, nitrogen (N), aluminum (Al), and boron (B) have been characterized using thermal admittance spectroscopy (AS) and deep level transient spectroscopy (DLTS). The temperature extrapolation of the results obtained by AS shows excellent agreement with those obtained by DLTS, yielding the base for an evaluation of incomplete ionization effects in SiC devices within usual operation ranges. The measured data has been analyzed using numerical drift-diffusion simulations based on the method of finite-elements. A numerical investigation of the different freeze-out characteristics of free carriers in p(+)n, n(+)p, and Schottky diodes shows that unlike in the case of B, the ionization time constant, of Al can be exclusively measured in the highly doped region of a p(+)n diode.