Defect dominant junction characteristics of 4H-SiC p(+)/n diodes

Forward and reverse current-voltage (I-V-T) measurements of MOCVD grown 4H-SiC p(+)/n diodes are compared to classical recombination-generation theory over the temperature range of 100 to 750 K. The forward bias data indicate that the I-V characteristics of the well-behaved devices follow a classical recombination dominant transport mechanism. Ideality factors were determined to be in the range of 1.85 to 2.09, and the forward activation energy found to be E(A)=1.56 eV compared to a nearly ideal value of 1.6 eV. A majority of the devices tested under forward bias conditions were, however, found to exhibit significant leakage current components due to tunneling at forward biases of up to 2.2 V for turn-on voltages in the 2.5 to 3.0 range. Deep level transient spectroscopy (DLTS) was also performed on the diode structures over the same wide temperature range, and the results were correlated to those obtained from reverse I-V-T and C-V-T characterization. Deep level defects at energies between 200 and 856 meV were identified from the DLTS data, and these levels are believed to be responsible for the tunneling dominant current conduction. Intrinsic deep levels, common to all devices tested, are emphasized and suggested as possible reverse bias tunneling paths for breakdown to explain the lack of an avalanche mechanism in all of the 4H-SiC diodes tested.