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Antimony ͑Sb͒, an isoelectronic impurity, has been studied as a surfactant during the lateral epitaxial overgrowth ͑LEO͒ of gallium nitride ͑GaN͒ by metalorganic vapor phase epitaxy ͑MOVPE͒. The presence of Sb in the gas phase was found to alter both the LEO growth rates and the predominant facet formations. Vertical facets to the LEO growth appear with the addition of Sb under conditions that normally produce triangular or sloped sidewalls over a range of growth temperatures. While Sb alters the growth facets, only a small amount of Sb was incorporated into the GaN, suggesting that Sb acts as a surfactant during the GaN MOVPE growth. Sb addition produces surface conditions characteristic of a Ga-rich surface stoichiometry indicating both a possible change in the reactivity of NH 3 and/or enhanced surface diffusion of Ga adatom species. © 2001 American Institute of Physics. ͓DOI: 10.1063/1.1415774͔The use of a suitable impurity, as a surfactant, during the growth of semiconductor films has attracted increasing interest in recent years. [1][2][3][4][5][6] Elemental surfactants are typically characterized by low vapor pressure and low solubility in the solid. They can segregate to the surface and affect surface properties, such as the surface energy, reconstruction and surface kinetic processes of the growing surface. As a result, a small amount of surfactant impurities can significantly alter the growth characteristics and change the resulting film structure without a high level of incorporation into the films. For example, in the case of SiGe growth, antimony ͑Sb͒ has been known to both segregate to the growth front and alter the surface energy of the SiGe. This change in surface energy results in an increase in the epitaxial thickness of the SiGe layer and facilitates layer by layer growth with respect to island growth. 1,2 In this letter, we describe the use of the Sb isoelectronic center as a surfactant during the lateral epitaxial overgrowth ͑LEO͒ of gallium nitride ͑GaN͒ by metalorganic vapor phase epitaxy ͑MOVPE͒.GaN and related materials have been extensively investigated for applications to short wavelength optoelectronics and high temperature and high power electronics. One of the main issues in the GaN crystal growth is the reduction in the threading dislocation density arising from the large lattice mismatch between the GaN film and underlying substrate. The LEO growth technique has been reported as a route for achieving GaN with a significant reduction in the dislocation density. Long-lifetime GaN laser diodes fabricated on LEOgrown materials have been demonstrated. 7 In these applications, it is desirable to increase the yield of the high quality GaN materials in the lateral overgrowth region. A high lateral overgrowth rate, as well as vertical facets, is typically chosen for smooth and rapid coalescence. 8 The growth and structure of LEO GaN materials have been studied through control of many growth parameters, such as the growth temperature, 9 mask orientation, 10,11 V/III ratio, 12 mask fill fact...

GaN 1ϪyAs y epitaxial alloy samples with ͓N͔ӷ͓As͔ were grown by metalorganic vapor phase epitaxy. The range of As content achieved, up to yϭ0.067, greatly extends the range of achievable As levels to values that are well within the miscibility gap of the GaN-GaAs system. The single-phase epitaxial nature of the alloy samples was confirmed by x-ray diffraction. The As-content dependence of the band gap was determined by optical absorption measurements. A highly-bowed bandgap was observed as a function of the As content, and a refined value of the bowing parameter of 16.9Ϯ1.1 eV was determined. © 2004 American Institute of Physics. ͓DOI: 10.1063/1.1652232͔The GaN 1Ϫy As y alloy at high N content is an attractive material for extending the wavelength range of GaN-based blue-light-emitting devices toward the red/infrared region. These alloys have a narrower band gap at smaller strain than InGaN alloys when grown on a GaN layer, due to the large band gap bowing parameter, which is attributed to a large difference in the atomic radii of N and As.1,2 These GaN 1Ϫy As y -based light emitters could replace GaAs-based long wavelength devices, thus reducing the use of As-based substrates and materials, and allowing multiwavelength light-emitting devices to be integrated on a single substrate. This alloy system, however, also possesses a large miscibility gap.3 Although some GaN 1Ϫy As y alloys with high N contents have been grown, 4 the realized As mole fraction ͑y͒ had been previously limited to yрϳ0.03. 5,6 Iwata et al. grew GaNAs alloys by gas source molecular beam epitaxy ͑MBE͒ over the composition range of 0Ͻyр0.0094 and determined a band gap bowing parameter.6 Gherasimova et al. also grew these alloys with As content up to 0.03 by metalorganic vapor phase epitaxy ͑MOVPE͒.5 Novikov et al. determined the MBE growth conditions to form the alloy over a limited range. 4 An As content of yу0.07 is, however, considered necessary for lasing wavelength of 650 nm in order to meet requirements for DVD applications. Moreover, the band gap of metastable GaN 1Ϫy As y , within the immiscible region has not been experimentally confirmed.In this letter, we denote GaN 1Ϫy As y on the N-rich side of the composition regime as GaNAs and GaN 1Ϫy As y on the As-rich side as GaAsN for simplicity. We successfully grew the GaN 1Ϫy As y alloy with As content, y, over the range of 0Ͻyр0.067. The optical band gap for the GaN 1Ϫy As y alloy was obtained from optical absorption experiments and its compositional dependence was determined.GaNAs layers were grown to a thickness of 0.25-1 m on GaN layers on sapphire substrates by low-pressure ͑76 Torr͒ MOVPE. The sources were trimethyl gallium ͑TMGa͒, ammonia (NH 3 ), and tertiarybutyl arsine (C 4 H 9 AsH 2 , TBAs͒. The flow rates were 16.3-49.0 mol/min for TMGa, 0.071-0.214 mol/min for NH 3 , and 26.3-937 mol/min for TBAs. The carrier gas was hydrogen (H 2 ). The growth temperature was 700-750°C and the growth rate was 0.9-2.7 m/h for the GaNAs layers. The high As content materials were obtained thro...

The role and effect of the isoelectronic center Sb on the structure and properties of GaN epilayers have been investigated. The gas phase Sb concentration was varied by changing the triethyl antimony/trimethyl gallium mole ratio over a wide range of concentrations while keeping other growth parameters constant. The Sb addition slightly improved the optical and structural properties of GaN epilayer at a low level of Sb incorporation, especially for the films grown under a high group V/III ratio conditions. The addition of Sb resulted in changes in GaN surface morphology, which was further explored by the lateral epitaxy overgrowth ͑LEO͒ technique through the changes in the growth rates and the facet formation. The presence of Sb in the gas phase greatly enhanced the lateral overgrowth rate and altered the formation of the dominant facets. Vertical facets to the LEO growth appeared with the addition of Sb under conditions that normally produced sloped sidewalls. While Sb altered the growth facet present during LEO, only a small amount of Sb was incorporated into the GaN, suggesting that Sb acts as a surfactant during the GaN metal organic vapor phase epitaxy growth. Sb addition produces surface conditions characteristic of a Ga-rich surface stoichiometry indicating both a possible change in the reactivity of NH 3 and/or enhanced surface diffusion of Ga adatom species in the presence of Sb.

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