Epitaxial GaN1−yAsy layers with high As content grown by metalorganic vapor phase epitaxy and their band gap energy

Abstract

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...

Highly mismatched crystalline and amorphous GaN1−xAsx alloys in the whole composition range

“…It was found that GaN doped with As at low, impurity like levels shows a characteristic blue emission at room temperature. At higher As doping levels an abrupt decrease in the band gap of resulting GaN 1-x As x alloys was observed [9,10,11,12]. Fig.…”

“…For both techniques, it is difficult to obtain a high concentration of As in the alloy before phase separation occurs. The 6 highest reported As content in MOVPE grown layers is x~0.067 [10,11,12] [21,22,23]. The atomic diffusion length in these non-equilibrium processes is long enough to form crystalline lattices with uniform compositions, but short enough to avoid equilibrium phase segregation.…”

“…For both techniques, it is difficult to obtain a high concentration of As in the alloy before phase separation occurs. The highest reported As content in MOVPE grown layers is x~0.067 [10,11,12]. Even lower maximum As contents of x~0.0026 [19] and x~0.01 [20] were achieved in MBE layers grown at .750 o C and at 500 o C, respectively Recently, materials with constituents having drastically different chemical or physical properties at compositions or structures far exceeding their thermodynamic solubility and stability limits have been synthesized using extreme non-equilibrium synthesis techniques [21,22,23].…”

Reactively sputtered GaAsxN1−x thin films

“…The smaller size of N allows its solubility in GaAs and extensive research has been reported on such alloys [3][4][5][6][7][8]. In comparison, owing to the larger size of As and consequent difficulty in the incorporation of As in GaN, very limited work has been reported on N-rich side of GaAs x N 1−x alloys, which have been mostly prepared by MOCVD and MBE [9,10]. N-rich GaAs x N 1−x alloys are important materials for extending the wavelength range of GaNbased blue light emitting devices towards the red/infrared region.…”

First-principle natural band alignment of GaN / dilute-As GaNAs alloy

“…5,[19][20][21][22][23][24][25][26][27][28] Li and co-workers first succeeded in incorporating As into thin film GaN through metal-organic chemical vapor deposition (MOCVD), and the redshift of band gap energy of the dilute-As GaNAs alloy was observed in the photoluminescence study. 5 Further studies have also shown successful incorporation of As-content up to 7% into GaN material through MOCVD, 20 and synthesis of GaNAs alloy in full composition range through molecular beam epitaxy (MBE) was recently reported. 21 Recent experimental work by Yu et al reported that the band gap of dilute-As GaNAs alloy reaches 2.3 eV ± 0.5 eV at roughly 6%-As impurities incorporation.…”