Interfacial effects during GaN growth on 6H-SiC (original) (raw)
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GaN Layers Grown by HVPE on P-type 6H-SiC Substrates
GaN, 1997
Gallium nitride films were successfully grown by HVPE technique on p-type 6H-SiC substrate. The layers exhibit high crystal quality as was determined by X-ray diffraction. Photoluminescence (PL) of these films was measured. The PL spectra were dominated by band edge emission. Concentration N d-N a in undoped epitaxial layers ranged from 2x10 17 to 1x10 1 9 cm-3. Mesa-structures formed by reactive ion etching showed good rectifying current-voltage characteristics for GaN/SiC pn heterojunctions.
Study of the optical and structural properties of GaN films grown on Si substrates with a SiC layer
Thin Solid Films, 2003
GaN films were grown on Si(100) substrates by molecular beam epitaxy employing an RF activated N-plasma source. The substrates were coated with a thin SiC layer to reduce the reaction of N with Si. The substrate temperature was set at 750 8C, and the flux of Ga atoms was varied by changing the Ga-Knudsen cell temperature (T) from 950 to 1100 8C. The effects of Ga the different growth conditions on the optical and structural characteristics of the films were studied by X-ray diffraction, atomic force microscopy, photoluminescence and photoreflectance spectroscopy. The results show that for T s950 8C, the films Ga presented a very poor crystal quality with a mixture of hexagonal (a) and cubic (b) GaN phases. By increasing T the crystal Ga quality improved. The films presented predominately the b-GaN phase for an optimal temperature T of 1050 8C.
Growth of GaN on porous SiC and GaN substrates
Journal of Electronic Materials, 2003
We have studied the growth of GaN on porous SiC and GaN substrates, employing both plasma-assisted molecular beam epitaxy (PAMBE) and metalorganic chemical vapor deposition (MOCVD). For growth on porous SiC, transmission electron microscopy (TEM) observations indicate that the epitaxial GaN growth initiates primarily from surface areas between pores, and the exposed surface pores tend to extend into GaN as open tubes and trap Ga droplets. The dislocation density in the GaN layers is similar to, or slightly less than, that observed in layers grown on non-porous substrates. For the case of GaN growth on porous GaN the overgrown layer replicates the underlying dislocation structure (although considerable dislocation reduction can occur as this overgrowth proceeds, independent of the presence of the porous layer). The GaN layers grown on a porous SiC substrate were found to be mechanically more relaxed than those grown on non-porous substrates; electron diffraction patterns indicate that the former are free of misfit strain or are even in tension after cooling to room temperature. Significant changes in the stress of the overgrown layers on porous GaN were also found, as seen in line shifts of low-temperature photoluminescence spectra.
Journal of Crystal Growth, 2005
High-quality GaN epitaxial films were successfully grown directly on 4H-SiC substrates. The difficulty in the nucleation as well as the overgrowth of GaN islands, which is often observed during metal-organic chemical vapor deposition, was solved using the concept of an epitaxial lateral overgrowth technique. The continuous mirror-flat GaN epitaxial film could be obtained at a reduced reactor pressure (76 Torr) and a lower N/Ga supply ratio. The full-width half-maximums (FWHMs) of the (0 0 0 2) and (1 01 3) rocking curves of the GaN epitaxial films on the 4H-SiC substrate at the optimized condition were 105 and 118 arcsec, respectively, under a skew symmetric diffraction geometry. The intense bound exciton lines with a FWHM of 10 meV and a free exciton peak appeared in the lowtemperature photoluminescence spectrum, illustrating the very high quality of the GaN film on 4H-SiC. r
Growth of GaN on SiC substrates by MBE
We report the growth of Al x Ga 1-x N alloys on (0001) sapphire by the method of Electron Cyclotron Resonance-assisted Molecular Beam Epitaxy (ECR-MBE). The films were doped n-type with silicon at carrier concentration levels from 10 16 to 10 19 cm -3 . SEM studies reveal smooth surface morphology consistent with the observed 3x4 surface reconstruction in the RHEED pattern. Independent determination of the Al-concentration and the lattice constant of the alloys shows that Vegard's rule is obeyed in the pseudo-binary GaN-AlN system. The bandgap of the alloys, determined by transmission and photoluminescence measurements, was found to depend linearly on Al-concentration.
Cubic GaN epilayers grown by molecular beam epitaxy on thin β-SiC/Si (001) substrates
Applied Physics Letters, 2000
The molecular beam epitaxy of cubic GaN on Si͑001͒ substrates, which were covered by a 4 nm thick -SiC layer, is reported. The structural and optical properties of the cubic GaN epilayers were studied by transmission electron microscopy, high-resolution x-ray diffraction, and low-temperature photoluminescence measurements. We find clear evidence for the growth of cubic GaN layers almost free of hexagonal inclusions. The density of extended defects and the near band edge photoluminescence of the cubic GaN layers grown at substrate temperatures of 835°C is comparable to that of high quality cubic GaN epilayers grown by molecular beam epitaxy on GaAs ͑001͒ substrates.
physica status solidi (a), 2001
High-quality GaN films were grown on Si(111) substrate using 3C-SiC intermediate layer by metalorganic chemical vapor deposition. The 3C-SiC intermediate layer was grown on the Si(111) substrate by chemical vapor deposition using tetramethylsilane as a single source precursor. We have investigated the effect of chemical etching of SiC intermediate layer surface under different conditions. SiC layer was etched using potassium carbonate (K 2 CO 3), hydrochloric acid (HCl), and hydrofluoric acid (HF), respectively. The surface roughness of 3C-SiC intermediate layer decreased as the chemical etching time was increased. GaN films with local atomically flat surfaces were obtained and the X-ray diffraction full-width at half maximum of (0002) peak was 664.5 arcsec for a 1.56 mm thick film. The reduced SiC surface roughness decreased the defect density in GaN epilayers. In the photoluminescence spectra at room temperature, the yellow band emission peak at around 2.2 eV disappeared.
Evidence for relaxed and high-quality growth of GaN on SiC(0001)
Applied Physics Letters, 1999
By using polarization-dependent x-ray absorption spectroscopy at the Ga edge, we study the growth of GaN on SiC͑0001͒ in the thickness range 0.7-150 nm. We find that the growth is always relaxed ͑i.e., nonpseudomorphic͒ even for the thinnest epilayers, i.e., below the expected critical thickness. No evidence is found for a mixed Ga/Si interface plane, while a C/N mixed interface plane cannot be ruled out. The results are discussed with reference to the electronic structure of the SiC/GaN heterojunction and in particular to band offsets and strain-induced piezoelectric polarization.
Fabrication and characterization of heterojunction diodes with HVPE-grown GaN on 4H-SiC
IEEE Transactions on Electron Devices, 2001
GaN/SiC heterojunctions can improve the performance considerably for BJTs and FETs. In this work, heterojunction diodes have been manufactured and characterized. The fabricated diodes have a GaN n-type cathode region on top of a 4H-SiC p-type epi layer. The GaN layer was grown with HVPE directly on off-axis SiC without a buffer layer. Mesa structures were formed and a Ti metallization was used as cathode contact to GaN, and the anode contact was deposited on the backside using sputtered Al. Both current-voltage (I-V) and capacitance-voltage (C-V) measurements were performed on the diode structures. The ideality factor of the measured diodes was 1.1 and was constant with temperature. A built in potential of 2.06 V was extracted from I-V-measurements and agrees well with the built in potential from C-V-measurements. The conduction band offset was extracted to 1.1 eV and the heterojunction was of type II. The turn on voltage for the diodes is about 1 V lower than expected and a suggested mechanism for this effect is discussed.