3C-SiC Heteroepitaxial Growth by Vapor-Liquid-Solid Mechanism on Patterned 4H-SiC Substrate Using Si-Ge Melt

International audienceIn this work, we report on the use of patterned 4H-SiC(0001) substrates for the heteroepitaxial growth of 3C-SiC by vapor-liquid-solid (VLS) mechanism using Ge(50)Si(50) melt. Mesas structures of various size and shape were obtained by standard photolithography and dry etching processes. On the temperature range investigated 1300-1450 degrees C, 3C-SiC deposit was obtained on top and outside the mesas. Some lateral enlargement of these mesas was observed, but it was systematically homoepitaxial. The lateral growth rate was found rather low compared to other techniques like chemical vapor deposition, with a maximum value of similar to 12 mu m/h. In addition, elimination of twin boundaries (TBs) inside the 3C-SiC deposit on top of the mesas was observed in the temperature range of 1400-1450 degrees C and for specific mesa shape or orientation of the sidewalls. The best case for eliminating these TBs was found to be with initially circular mesas, which spontaneously form well orientated hexagonal facets and then lead to TB-free deposit on top after VLS growth

Splitting of close N-Al donor-acceptor-pair spectra in 3C-SiC

Discrete series of lines have been observed for many years in N-Al DAP (Donor Acceptor Pair) spectra in 3C-SiC. Unfortunately, up to now, there has been no quantitative analysis for the splitting of lines in a given shell. This is done in this work for N-Al DAP spectra in 3C-SiC. The samples were non-intentionally doped 3C-SiC layers grown by CVD on a VLS seeding layer grown on a 6H-SiC substrate. From low temperature photoluminescence measurements, strong N-Al DAP emission bands were observed and, on the high energy side of the zero-phonon line, we could resolve a series of discrete lines coming from close pairs. Comparing with literature data, we show that the splitting energy for a given shell is constant and, to explain this shell substructure, we consider the non equivalent sets of sites for a given shell. Results are discussed in terms of the ion-ion interaction containing third and forth multipole terms

Effects of Growth Conditions on the Low Temperature Photoluminescence Spectra of (111) 3C-SiC Layers Grown by Chemical Vapor Deposition on 3C-SiC Seeds grown by the Vapor-Liquid-Solid Technique

We report the results of a low temperature photoluminescence investigation of 3C-SiC samples grown by chemical vapor deposition on vapor-liquid-solid seeds. The main parameters tested in this series of samples were i degrees) the effects of changing the C/Si ratio and ii degrees) the growth temperature on the final growth product. On the first series the C/Si ratio varied from 1 to 14 for a constant growth temperature of 1550 C. For the second series, the growth temperature varied from 1450 to1650 degrees C by steps of 50 degrees C with a constant C/Si ratio equal to 3. According to this work, the best results (minimum incorporation of impurities and best crystal quality) were obtained when using a C/Si ratio of 3 at 1650 degrees C

Nondestructive Evaluation of Photo-Electrical Properties of 3C-SiC (111) Homoepitaxial Layers Grown by CVD

International audienceFree carrier absorption (FCA) and picosecond light-induced transient grating (LITG) techniques were applied to study the photoelectrical properties of 3C-SiC(111) homoepitaxial layers grown by CVD method on VLS (vapour-liquid-solid) grown seeds. The thickness of the CVD layers was ~10.5 µm with non-intentional type doping of n (~ 1017 cm-3) or p (<1015 cm-3). The carrier lifetime and the diffusion coefficient were measured as the function of the sample temperature, the injected excess carrier density at different growth parameters. At room temperature the ambipolar diffusion coefficient was Da=2.5-3 cm2/s, while the lifetime was in the range of 12-18 ns. The best structural and electrical properties were obtained for a CVD layer grown at high, 1600 °C temperature

Splitting of close N-Al donor-acceptor-pair spectra in 3C-SiC

Discrete series of lines have been observed for many years in N-Al DAP (Donor Acceptor Pair) spectra in 3C-SiC. Unfortunately, up to now, there has been no quantitative analysis for the splitting of lines in a given shell. This is done in this work for N-Al DAP spectra in 3C-SiC. The samples were non-intentionally doped 3C-SiC layers grown by CVD on a VLS seeding layer grown on a 6H-SiC substrate. From low temperature photoluminescence measurements, strong N-Al DAP emission bands were observed and, on the high energy side of the zero-phonon line, we could resolve a series of discrete lines coming from close pairs. Comparing with literature data, we show that the splitting energy for a given shell is constant and, to explain this shell substructure, we consider the non equivalent sets of sites for a given shell. Results are discussed in terms of the ion-ion interaction containing third and forth multipole terms

Evolution of 3C-SiC islands nucleated from a liquid phase on Si face alpha-SiC substrates

International audienceThe contact between alpha-SiC crystals and Si-Ge based melts provokes the nucleation of 3C-SiC islands on the crystal surface. Evolution of these islands as a function of various parameters was studied. On both 4H and 6H substrates, it was found that, after nucleation, 3C-SiC islands first enlarge and may form a complete 3C layer under certain conditions. The 3C deposit can then be dissolved by the liquid phase at high temperature or for prolonged contact at relatively moderate temperature. The graphite crucible is proposed to play a central role in these enlargement and dissolution mechanisms by providing extra carbon atoms on the seed surface (enlargement) or provoking thermal induced carbon transport toward the sidewall (dissolution). Several differences between the use of 4H and 6H substrates were also observed. (C) 2009 Elsevier BM. All rights reserved

Study of the 3C-SiC nucleation from a liquid phase on a C face 6H-SiC substrate

International audienceThe early stage of 3C-SiC nucleation and islands enlargement on on-axis 6H-SiC(000 (1) over bar) (C face) were studied by changing the conditions of interaction of a Si(0.25)Ge(0.75) melt with the SiC substrate. After changing the temperature or the plateau duration at a fixed temperature, evolution in terms of shapes and sizes of the 3C-SiC islands was found. The observed islands enlargement in the early stage of interaction was explained by taking into account a carbon transport from the graphite crucible to the seed. Once the crucible reached its thermal and thermodynamical equilibrium with the liquid, the islands started to be dissolved inside the melt due to a possible but small thermal gradient from the seed (hotter) to the sidewalls of the crucible (colder). By adding propane in the gas phase before reaching this equilibrium, SiC growth by vapour-liquid-solid (VLS) mechanism was achieved and the 3C-SiC layers thus obtained were always found to contain a high density of twins. This is probably due to the fact that the density of 3C nuclei, after interaction between the SiGe melt and the SiC seed, was always very high which should prevent orientation selection, unlike the case of Si face. (c) 2009 Elsevier B.V. All rights reserved

Effects of Growth Conditions on the Low Temperature Photoluminescence Spectra of (111) 3C-SiC Layers Grown by Chemical Vapor Deposition on 3C-SiC Seeds grown by the Vapor-Liquid-Solid Technique

We report the results of a low temperature photoluminescence investigation of 3C-SiC samples grown by chemical vapor deposition on vapor-liquid-solid seeds. The main parameters tested in this series of samples were i degrees) the effects of changing the C/Si ratio and ii degrees) the growth temperature on the final growth product. On the first series the C/Si ratio varied from 1 to 14 for a constant growth temperature of 1550 C. For the second series, the growth temperature varied from 1450 to1650 degrees C by steps of 50 degrees C with a constant C/Si ratio equal to 3. According to this work, the best results (minimum incorporation of impurities and best crystal quality) were obtained when using a C/Si ratio of 3 at 1650 degrees C

LTPL investigation of N-Ga and N-Al donor-acceptor pair spectra in 3C-SiC layers grown by VLS on 6H-SiC substrates

Ga-doped 3C-SiC layers have been grown on on-axis 6H-SiC (0001) substrates by the VLS technique and investigated by low temperature photoluminescence (LTPL) measurements. On these Ga-doped samples, all experimental spectra collected at 5K were found dominated by strong N-Ga donor-acceptor pair (DAP) transitions and phonon replicas. As expected, the N-Ga DAP zero-phonon line (ZPL) was located at lower energy (similar to 86 meV) below the N-Al one. Fitting the transition energies for the N-Al close DAP lines gave 251 meV for the Al acceptor binding energy in 3C-SiC and, by comparison, 337 meV for the Ga acceptor one