S.G. Sridhara

Luminescence from stacking faults in 4H SiC

A previously unreported photoluminescence spectrum observed in certain 4H SiC bipolar diodes after extended forward voltage operation is reported. We assign this emission to exciton recombination at local potential fluctuations caused by stacking faults, which are created during operation of the diodes. Possible recombination mechanisms responsible for the spectrum are discussed.

Pseudodonor nature of the DI defect in 4H-SiC

We use the recent findings about the pseudodonor character of the DI defect to establish an energy-level scheme in the band gap for the defect, predicting the existence of a hole trap at about 0.35 eV above the valence band. Using minority carrier transient spectroscopy, we prove that the DI defect indeed is correlated to such a hole trap. In addition, we show that the DI defect is not correlated to the Z1/2 electron trap, in contrast to what was previously reported.

Ion implantation of silicon carbide

Ion implantation is an important technique for a successful implementation of commercial SiC devices. Much effort has also been devoted to optimising implantation and annealing parameters to improve the electrical device characteristics. However, there is a severe lack of understanding of the fundamental implantation process and the generation and annealing kinetics of point defects and defect complexes. Only very few of the most elementary intrinsic point defects have been unambiguously identified so far. To reach a deeper understanding of the basic mechanisms SiC samples have been implanted with a broad range of ions, energies, doses, etc., and the resulting defects and damage produced in the lattice have been studied with a multitude of characterisation techniques. In this contribution we will review some of the results generated recently and also try to indicate where more research is needed. In particular, deep level transient spectroscopy (DLTS) has been used to investigate point defects at very low doses and transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS) are used for studying the damage build-up at high doses.

Dll PL Intensity Dependence on Dose, Implantation Temperature and Implanted Species in 4H- and 6H-SiC

In most semi-conductor processing ion implantation is a key technology. The drawback of ion implantation is that a great deal of lattice defects, such as vacancies, interstitials, anti sites and complexes, are introduced. The annealing behaviour of these defects is important for the viability of ion implantation as a commonly used method. In SiC a defect that is only seen after ion implantation and not after irradiation with neutrons or electrons is the D-II defect. The use of Si or C as implanted species have made it possible to investigate the D-II photoluminescence (PL) intensity dependence on an excess of either of the two constituents in SiC. The effect of performing a hot implant at 600degreesC compared to a room temperature implant was also looked into. The D-II PL intensity was measured after a 1500degreesC anneal. When the implantation was performed at room temperature the C implanted samples showed a significantly higher D-II luminescence than the Si implanted. This makes it tempting to assume that a surplus of C and likely C interstitials are involved in the defect formation. However, when the implantation is done at 600degreesC the difference between Si and C implanted samples almost disappears and a slightly higher D-II intensity can be seen in the Si implanted samples. This effect may be due to the mobility of C interstitials at temperatures above 500degreesC. This clearly demonstrates the effect of hot implantation that there is a major change in D-II PL intensity even after a 1500degreesC anneal.