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Argon ions were implanted into n-type 6H-SiC epitaxial layers at 600°C. Postimplantation annealing was carried out at 1,600°C for 5 min in an Ar ambient. Four implantation-induced defect levels were observed at EC-0.28 eV, EC-0.34 eV, EC-0.46 eV, and EC-0.62 eV by deep level transient spectroscopy. The defect center at EC-0.28 eV is correlated with ED1/ED2 and with ID5. The defect at EC-0.46 eV with a capture cross section of 7.8 × 10−16 cm2 is correlated with E1/E2, while the defect at EC-0.62 eV with a capture cross section of 2.6 × 10−14 cm2 is correlated with Z1/Z2. Photo deep level transient spectroscopy was also used to study these defects. Upon illumination, the amplitudes of the deep level transient spectroscopy (DLTS) peaks increased considerably. Two emission components of Z1/Z2 were revealed: one fast and the other slow. The fast component could only be observed with a narrow rate window. In addition, a new defect was observed on the low-temperature side of the defect at EC-0.28 eV when the sample was illuminated.

Shallow impurities are the principal means of affecting the electrical properties of semiconductors in order to induce desired characteristics. They can be used to isolate a region by introducing carriers of opposite charge, or they can be used to enhance the number of carriers of a particular type. Thermal admittance spectroscopy has been used to determine the activation energies of the principal p-type dopants, Al and B, in 4H and 6H-SiC, and temperature dependent Hall effect measurements were used to study the shallow B acceptors in 6H-SiC. The accept or species B and Al occupy inequivalent lattice sites in the Si sublattice, and would be expected to exhibit distinct energy levels for each site in analogy to the well known donor energy levels of N. Activation energies for B in 6H-SiC were found to be Eh=Ev+0.27 eV, Ek1=Ev+0.31 eV, and Ek2=Ev+0.38 eV. Al acceptors in 4H-SiC were found to exhibit two energy levels at Eh=Ev+0.212 eV and Ek=Ev+0.266 eV.

The electronic properties of heavily doped n-type 4H, 6H, and 15R SiC have been studied with temperature dependent Hall effect, resistivity measurements, and thermal admittance spectroscopy experiments. Hopping conduction was observed in the resistivity experiments for samples with electron concentrations of 1017 cm−3 or higher. Both band and hopping conduction were observed in all three polytypes in resistivity and Hall effect experiments. The hopping conduction activation energy e3 obtained from the resistivity measurements varied from 0.003 to 0.013 eV. The e3 value obtained from thermal admittance spectroscopy measurements were slightly lower. The nitrogen ionization levels were observed by thermal admittance spectroscopy only in those samples where hopping conduction was not detected by this experiment. Free carrier activation energy Ea for nitrogen was difficult to determine from temperature dependent Hall effect measurements because of the effects of hopping conduction. A new feature in the apparent carrier concentration vs inverse temperature data in the hopping regime was observed.

The electronic properties of boron in bulk 6H-SiC have been studied by temperature dependent Hall effect, thermal admittance spectroscopy, and optical absorption. A single acceptor level located between 0.27 and 0.35 eV above the valence band is associated with boron on a silicon lattice site. The deep nature of this acceptor level prevents complete thermal activation of the level at room temperature and thus carrier concentration measurements at this temperature will not give the total boron concentration. A spread in the measured activation energy for boron is reported. Measurement of optical absorption is suggested as a nondestructive measure of boron concentration. No evidence for the D-center was observed in this material.

Deep levels have been identified and characterized in undoped Si1−xGex alloys grown on silicon substrates by gas-source molecular beam epitaxy. Hole traps in the p-type layers have activation energies ranging from 0.029–0.45 eV and capture cross sections (σ∞ ranging from 10−9 to 10−20 cm2. Possible origins of these centers are discussed.

A new method of forming electrical contacts on high purity p-type silicon has been developed. The resultant contacts are ohmic from 18 to 300K. The electrical sparking technique permits localized doping in the contact region of the device while avoiding the over-all high annealing temperatures required by diffusion. Indium solder is used for metallization and attachment of wires to the sparked regions. The process is simple and easily applied to samples for measuring electrical transport properties or to devices, such as silicon solar cells.