The influence of nitridation time on the structural properties of GaN grown on Si (111) substrate (original) (raw)
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Microstructure of GaN Grown on (111) Si by MOCVD
Mrs Internet Journal of Nitride Semiconductor Research, 1999
Gallium nitride was grown on (111) Si by MOCVD by depositing an AlN buffer at 1080°C followed by GaN at 1060°C. The 2.2 µm layer cracked along {1-100} planes upon cooling to room temperature, but remained adherent. We were nonetheless able to examine the material between cracks with TEM. The character and arrangement of dislocations are much like those of GaN grown on Al 2 O 3 : ~2/3 pure edge and ~1/3 mixed (edge + screw), arranged in boundaries around domains of GaN that are slightly misoriented with respect to neighboring material. The 30 nm AlN buffer is continuous, indicating that AlN wets the Si, in contrast to GaN on Al 2 O 3 .
MRS Proceedings, 2005
An alternative scheme to the growth of crack free, dislocation reduced III-Nitride layers on Silicon substrate has been previously introduced that relies on formation of an ion implanted defective layer in the substrate with implantation taking place in the presence of AlN buffer layer. Here, the effects of N+ ion implantation of AlN/Si (111) substrate on the structural and optical properties of the overgrown GaN epilayers have been investigated. Temperature dependent photoluminescence has been used to investigate the impact of the implantation conditions (energy and dose) on optical and structural quality of the GaN overgrown layers. A correlation between PL and high resolution x-ray diffraction (XRD) of the overgrown GaN layers show that the lowest FWHM of bandedge, the highest bandedge to deep defect blue luminescence band ratio, and the lowest symmetric rocking curve FWHM are achieved for the optimized implantation conditions. This correlates well with the results of etch pit de...
Journal of Crystal Growth, 2000
GaN layers are grown by metalorganic chemical vapor deposition (MOCVD) on Si(1 1 1) substrates. X-ray di!raction (XRD) measurements and cross-section transmission electron microscopy (TEM) show a comparable crystalline quality of the samples to the quality of GaN/sapphire samples. Both the characteristic symmetric GaN(0 0 0 2) and the asymmetric GaN(1 0!1 5) X-ray re#ections have full-widths at half-maximum of 600}700 arcsec. The dislocation density as estimated from TEM investigation is found to be of the order of 10 cm\. The initially deposited AlAs nucleation layer is transformed into AlN by supplying ammonia to the AlAs layer. This bu!er layer can be completely etched o! thus providing an easy way for substrate-layer separation after growth, an essential step for avoiding absorption of radiation emitted from nitride layers in the silicon substrate.
Growth of dislocation-free GaN islands on Si(111) using a scandium nitride buffer layer
Journal of Crystal Growth, 2007
Gallium nitride was deposited using metal-organic vapour-phase epitaxy (MOVPE) on Si(1 1 1) substrates, using buffer layers of scandium nitride grown by gas-source molecular beam epitaxy (GS-MBE). A series of ScN buffer layers with varying roughness, thickness and crystallinity were used. The buffer layer crystallinity was shown to affect the morphology, residual strain and crystallinity of the subsequently grown GaN as well as the degree of wetting of ScN by GaN. The orientation of the GaN with respect to the ScN and the Si substrate was (0 0 0 1) GaN J(1 1 1) ScN J(1 1 1) Si , [0 1 1 0] GaN J[1 1 2] ScN J[2 1 1] Si . GaN grown directly onto ScN buffer layers at 1020 1C displayed island growth with limited wetting of the ScN. The reduced ScN-GaN interfacial area resulted in the growth of dislocation-free GaN islands of several microns in diameter. Predeposition of small amounts of GaN on the ScN at either 750 or 540 1C promoted wetting of the ScN by GaN and hence increased coalescence, allowing a continuous film to form; however, the increased ScN-GaN interfacial area resulted in the presence of threading dislocations. These were predominantly screw and mixed-type dislocations. r
Applied Surface Science, 2016
A single-crystalline with high quality of gallium nitride epilayers was grown on silicon (1 1 1) substrate by metal organic chemical vapor deposition. The process of nitridation surface treatment was accomplished on silicon (1 1 1) substrate by flowing the ammonia gaseous. Then, it was followed by a thin aluminum nitride nucleation layer, aluminum nitride/gallium nitride multi-layer and a thick gallium nitride epilayer. The influence of in situ nitridation surface treatment on the crystallinity quality of gallium nitride epilayers was studied by varying the nitridation times at 40, 220 and 400 s, respectively. It was shown that the nitridation times greatly affect the structural properties of the grown top gallium nitride epilayer on silicon (1 1 1) substrate. In the (0 0 0 2) and (1 01 2) X-ray rocking curve analysis, a narrower value of full width at half-maximum has been obtained as the nitridation time increased. This is signifying the reduction of dislocation density in the gallium nitride epilayer. This result was supported by the value of bowing and root mean square roughness measured by surface profilometer and atomic force microscopy. Furthermore, a crack-free gallium nitride surface with an abrupt cross-sectional structure that observed using field effect scanning electron microscopy was also been obtained. The phi-scan curve of asymmetric gallium nitride proved the top gallium nitride epilayer exhibited a single-crystalline structure.
Current Applied Physics, 2009
In the present paper, the effects of nitridation on the quality of GaN epitaxial films grown on Si(1 1 1) substrates by metal-organic chemical vapor phase deposition (MOCVD) are discussed. A series of GaN layers were grown on Si(1 1 1) under various conditions and characterized by Nomarski microscopy (NM), atomic force microscopy (AFM), high resolution X-ray diffraction (HRXRD), and room temperature (RT) photoluminescence (PL) measurements. Firstly, we optimized LT-AlN/HT-AlN/Si(1 1 1) templates and graded AlGaN intermediate layers thicknesses. In order to prevent stress relaxation, step-graded AlGaN layers were introduced along with a crack-free GaN layer of thickness exceeding 2.2 lm. Secondly, the effect of in situ substrate nitridation and the insertion of an Si x N y intermediate layer on the GaN crystalline quality was investigated. Our measurements show that the nitridation position greatly influences the surface morphology and PL and XRD spectra of GaN grown atop the Si x N y layer. The X-ray diffraction and PL measurements results confirmed that the single-crystalline wurtzite GaN was successfully grown in samples A (without Si x N y layer) and B (with Si x N y layer on ). The resulting GaN film surfaces were flat, mirror-like, and crack-free. The full-width-at-half maximum (FWHM) of the X-ray rocking curve for (0 0 0 2) diffraction from the GaN epilayer of the sample B in x-scan was 492 arcsec. The PL spectrum at room temperature showed that the GaN epilayer had a light emission at a wavelength of 365 nm with a FWHM of 6.6 nm (33.2 meV). In sample B, the insertion of a Si x N y intermediate layer significantly improved the optical and structural properties. In sample C (with Si x N y layer on Al 0.11 Ga 0.89 N interlayer). The in situ depositing of the, however, we did not obtain any improvements in the optical or structural properties.
Materials Science in Semiconductor Processing, 2013
The strain analysis of GaN film on nitridated Si(111) substrate with different growth times between 0 and 660 s via metal organic chemical vapor deposition (MOCVD) was conducted based on the precise measurement of the lattice parameters by using highresolution X-ray diffraction (HR-XRD). The nitridation time (NT) was changed at a fixed growth condition. The a-and c-lattice parameters were measured, followed by the in-plane and out-of-plane strains. Then, the biaxial and hydrostatic components were extracted from the total strain values obtained, and were then discussed in the present study as functions of the NT. The biaxial strain and stress are also strongly affected by the non-uniformity of the SiN x buffer layer thickness.
Reduction of dislocation density in heteroepitaxial GaN: role of SiH4 treatment
Journal of Crystal Growth, 2004
TEM and AFM data show that a significant reduction of threading dislocations in heteroepitaxial GaN/Al 2 O 3 grown by MOCVD has been achieved. The reduction has been obtained by growth interruption followed by annealing in silane (SiH 4 ). Density of threading dislocations in the GaN layer above the silane-exposed surface decreased to 5 Â 10 7 cm À2 in comparison to 10 9 cm À2 in the layer below this surface. TEM data showed the existence of pyramidal pits at the silane-exposed surface. They were overgrown by the subsequent GaN layer. The presence of these pits indicates that the GaN surface was selectively etched during the silane flow. These pits were sites where dislocations drastically changed propagation direction from parallel to the c-axis to horizontal. Horizontal propagation of dislocations above the surface treated by silane (where formation of SiN was expected) suggests that the GaN layer in this region was grown in the lateral epitaxial overgrowth mode. EDX measurements performed at the interface between the SiH 4 -treated GaN layer and the subsequently grown GaN did not show any presence of Si. Therefore, it is believed that the dislocation reduction is related to the lateral overgrowth above the pits and not to the formation of a SiN interlayer. r
Journal of Crystal Growth, 2002
We studied the initial growth of Si-doped GaN (GaN:Si) epilayers grown under both N-and Ga-rich conditions. Upon Si doping, the surface polarity changed from N-to Ga-polarity. The surface diffusion kinetics of the Ga adatoms of the GaN:Si epilayers depended strongly on the Ga/N flux ratio. GaN:Si films with good crystal quality were obtained for a Ga/N flux ratio slightly larger than 1. The dislocation density decreased about one order of magnitude, while the stacking fault and cubic phase density near the interfacial region increased. The main types of dislocations in the undoped GaN were mixed and edge dislocations. In the GaN:Si, the main dislocations were pure-edge dislocations. The dislocation-density reduction in the GaN:Si may have been due to a low density of mixed dislocations in the presence of a high density of stacking faults and cubic phase.
Epitaxial lateral overgrowth of non-polar GaN(11̄00) on Si(112) patterned substrates by MOCVD
Journal of Crystal Growth, 2011
m-Plane GaN was grown selectively by metal-organic chemical vapor deposition (MOCVD) on patterned Si(1 1 2) substrates, where grooves aligned parallel to the Si/1 1 0S direction were formed by anisotropic wet etching to expose the vertical Si{1 1 1} facets for growth initiation. The effect of growth conditions (substrate temperature, chamber pressure, and ammonia and trimethylgallium flow rates) on the growth habits of GaN was studied with the aim of achieving coalesced m-plane GaN films. The epitaxial relationship was found to be GaN(1 1 0 0) 99 Si(1 1 2), GaN[0 0 0 1] 99 Si[1 1-1], GaN[1 1 2 0] 99 Si[1 1 0]. Among all growth parameters, the ammonia flow rate was revealed to be the critical factor determining the growth habits of GaN. The distribution of extended defects, such as stacking faults and dislocations, in the selectively grown GaN were studied by transmission electron microscopy in combination with spatially resolved cathodoluminescence and scanning electron microscopy. Basal-plane stacking faults were found in the nitrogen-wing regions of the laterally overgrown GaN, while gallium-wings were almost free of extended defects, except for the regions near the GaN/Si{1 1 1} vertical sidewall interface, where high dislocation density was observed.