Origin and anomalous behavior of dominant defects in 4H-SiC studied by conventional and Laplace deep level transient spectroscopy

Ł. Gelczuk , Maria Dąbrowska-Szata , Valery Kolkovsky , Mariusz Sochacki , Jan Szmidt , Teodor Gotszalk

Abstract

Several deep level defects were observed by conventional deep level transient spectroscopy (DLTS) and high-resolution Laplace DLTS (LDLTS) in n-type 4H-SiC junction barrier Schottky diodes. We have shown that the broad DLTS peak labeled Z_1/2 has, in fact, two components, Z₁ and Z₂, with activation enthalpies for electron emission of 0.63 eV and 0.68 eV, respectively. The reorientation process between these two components was observed. A combination of double-correlated DLTS and LDLTS demonstrated an anomalous reduction of the emission rate and an increase of the activation enthalpy of Z₂ with an increase of the reverse bias applied to the diode. The possible explanation of this phenomenon could be correlated with a tensile stress in epitaxial SiC layers. The results observed are discussed in the frame of the model that correlates Z₁ and Z₂ with carbon vacancies (V_C), located at hexagonal (h) and cubic (k) lattice sites, respectively. We also discussed the origin of other traps E₀-E₅ with particular emphasis on a N-related shallow donor level located at 0.04 eV below the conduction band, which has never been previously reported by DLTS studies.