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Ohmic contacts to the top p-type layers of 4H-SiC p + –n–n + epitaxial structures having an acceptor concentration lower than 1×10 19 cm −3 were fabricated by the rapid thermal anneal of multilayer Al/Ti/Pt/Ni metal composition. The rapid thermal anneal of multilayer A1/Ti/Pt/Ni metal composition led to the formation of duplex cermet composition containing Ni 2 Si and TiC phases. The decomposition of the SiC under the contact was found to be down to a depth of about 100 nm. The contacts exhibited a contact resistivity R c of 9×10 −5 Ω cm −2 at 21°C, decreasing to 3.1×10 −5 Ω cm −2 at 186°C. It was found that thermionic emission through the barrier having a height of 0.097 eV is the predominant current transport mechanism in the fabricated contacts.

An AlSi-based ohmic contact with a new composition is reported in this paper. AlSi(2%)Ti(0.15%) contacts are formed by evaporation on p-type 4H-SiC grown by liquid phase epitaxy (LPE) and annealed in the temperature range from 700 to 950°C. The ohmic behaviour has been checked by I–V characteristics and the contact resistivity has been measured by the linear transmission-line-model (TLM) method. The dependence of the contact resistivity on the annealing conditions has been studied. An ohmic behaviour has been established at 700°C while the lowest contact resistivity value of 9.6×10 −5 Ω cm 2 has been obtained after annealing at 950°C. The thermal stability of both Al/Si/SiC and AlSiTi/SiC contacts at a temperature of 600°C has been studied. It has been found that the AlSiTi/SiC contacts are stable for 100 h at this ageing temperature while the Al/Si/SiC contacts deteriorate after 24 h.

A new approach for overcoming the problems of the heteroepitaxial β-SiC growth on Si substrates is hereby proposed. Namely, the surfactant effect is investigated by using Ge as adsorbate. The better control of the Si-surface conversion to SiC is targeted (conversion process). A structure is proposed taking into account eventual incorporation of the Ge in the SiC lattice. The growth experiments towards the proposed structure were performed by solid source MBE and the grown samples were ex-situ characterized by atomic force microscopy (AFM). In all cases, a clear difference between samples grown with and without the Ge adsorbate layer is observed.

This work combines the advantages of two techniques, MBE and LPCVD, to grow epitaxial 3C-SiC films on 2 in. Si (001) wafers misoriented 2–4° towards [110]. For comparison, SiC was also deposited on bare Si (001) wafers. The LPCVD process was performed in a hot-wall quartz reactor at temperatures below 1200°C using an organometallic compound, tetramethylsilane, as a single precursor. The effect of the MBE buffer layer on the LPCVD SiC film quality has been investigated mainly by transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The best LPCVD SiC films were achieved at 1170°C. These preliminary results show that the presence of the MBE carbonization layer improves the LPCVD subsequent growth. The LPCVD SiC layer is highly sensitive to the quality of the buffer layer.

The quality of Al/Ti-based ohmic contacts formed on 4H–SiC films under various annealing conditions has been examined. Atmospheric, vacuum and high vacuum environments as well as resistive, inductive and rapid thermal heating have been used. Vacuum annealing resulted in non-oxidized contacts independent of the heating method. The ohmic contacts were fabricated on both highly doped (1×1018 cm−3) CVD-grown and extremely high doped (>1×1020 cm−3) LPE-grown films. Reproducible and of low specific contact resistance (∼1×10−4 Ω cm2) contacts were obtained only for the case of LPE-grown films.

The structural characteristics of gold/3C-SiC contacts, subjected to a long annealing at 500 °C for 500 h for aging investigation, were studied by transmission electron microscopy. After the aging test about 50% of the gold which was deposited on the SiC surface was diffused through the 2.5 μm thick 3C-SiC to the SiC/Si interface forming an almost continuous gold film resulting in a SiC/Au/Si structure. The intermediate gold film is in perfect epitaxial relation to the 3C-SiC overgrown and the Si substrate, in spite of the 25% misfit between the Au and Si. Moire fringes produced by the interference of the Au and Si lattices reveal that the two lattices are perfectly relaxed. No linear or planar defects were observed in the gold film. No Au precipitates were observed inside the 3C-SiC overgrown or in the Si-substrate. A mechanism responsible for the formation of the intermediate gold film in the SiC/Si interface is proposed.

The properties of SiC have great potential for high temperature electronic device applications. For the realization of these devices the formation of stable (at elevated temperatures), low resistance ohmic contacts is required. For this purpose, multiple metallization schemes have been investigated on 3C-SiC grown on Si substrates by the chemical vapor deposition method. Both thick layers and thin multilayers of metals, deposited by electron beam evaporation, have been studied. Most of the metallizations exhibited ohmic behavior as-deposited even for relatively low doping levels due to the high concentration of defects in the SiC films. Annealing at temperatures up to 850 °C and ageing tests up to 550 °C were used to examine their thermal stability. The use of Al as contact overlayer instead of Au resulted in more stable contacts. The Cr/Ti/Pt/Mo/Al metal scheme produced the best results. On samples with doping (1–3) × 10 17 cm −3 an R c = 5.5 × 10 −6 Ω cm 2 was obtained while on samples with doping 3 × 10 18 cmu−3 an R c = 6 × 10 −7 Ωcm 2 before ageing and 7 × 10 −5 Ωcm 2 after 400 h at 550 °C was observed.

The carbonization of Si(100) surfaces exposed to a sublimed carbon beam at low substrate temperatures in a molecular beam epitaxy system was studied. Different carbon sublimation rates and substrate temperatures were used. The films were analyzed using in situ (reflected high energy electron diffraction and Auger surface analysis) and ex-situ (scanning electron microscopy and Fourier transform IR spectroscopy) methods. The results of the analysis showed that single-crystalline β-SiC can be grown by this technique. In addition, the Si-to-SiC conversion temperature limit was determined to be 600–650 °C, which is the lowest reported value, regardless of the growth method.

Deep levels in undoped semi-insulating In 0.52 Al 0.48 As layers grown by molecular beam epitaxy on iron-doped InP have been studied by photoluminescence and photo-induced current transient spectroscopy. The effect of the growth temperature T g in the range from 300 o C to 530 o C has been investigated. The results show that low T g causes the material quality to deteriorate and leads to formation of a higher concentration of deep traps. It is shown that optimized material quality can be obtained For InAlAs layers on InP substrates with T g around 530 o C with sufficiently high resistivity, reduced trap density and good structural properties which is appropriate for fabrication of high electron mobility transistors

The aim of this work is to show that room temperature photoreflectance can give the same indications as low temperature photoluminescence about the crystalline quality of both layers and interfaces. Our samples consist of molecular beam epitaxy InAlAs layers lattice-matched to InP substrates, grown at different growth temperatures and using different InP cleaning temperatures. The photoreflectance broadening parameter (γ) has been determined and compared with the well-known linewidth broadening of the photoluminescence. Both methods indicate that the best InAlAs crystalline quality is obtained for a growth temperature of 530 ° and an InP surface cleaning temperature of 530 °.