N-rich GaNAs with High As Content Grown by Metalorganic Vapor Phase Epitaxy
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N-rich GaNAs with High As Content Grown by Metalorganic Vapor Phase Epitaxy Akitaka Kimura*, H. F. Tang, C. A. Paulson1, and T. F. Kuech Department of Chemical and Biological Engineering, The University of Wisconsin-Madison, Madison, WI 53706-1691, USA 1 Department of Electrical and Computer Engineering, The University of Wisconsin-Madison, Madison, WI 53706-1691, USA ABSTRACT GaN1-yAsy epitaxial alloys on the N-rich side with high As content were grown by metalorganic vapor phase epitaxy. They had specular surfaces and the single-phase epitaxial nature was confirmed by X-ray diffraction. The As incorporation increased through both a decrease in the growth temperature and V/III ratio. These trends were similar to that found in other III-V alloy systems which exhibit a large miscibility gap and the anion incorporation was considered to have been limited kinetically under the conditions of the low V/III ratio. The range of achieved As content was extended up to y=0.067, which is a composition well within the miscibility gap. The As-content dependence of the band gap energy was determined by optical absorption measurements and large bowing parameter of 16.8 ± 0.9 eV was determined. INTRODUCTION The wurzite or hexagonal (h-) GaNAs alloy on the N-rich side is an attractive material for extending the wavelength range of GaN-based blue-light-emitting devices toward the red or infrared region. These alloys have a narrower band gap at a smaller strain than InGaN alloys, when grown on a GaN layer, due to the large band gap bowing parameter [1, 2], which is attributed to a large difference in the atomic radii of N and As. These GaNAs-based light emitters could replace GaAs-based long wavelength devices, reducing the use of As-based substrates and materials, and allowing multi-wavelength light-emitting devices to be integrated on a single substrate. This alloy system, however, also possesses a large miscibility gap [3]. Although GaN1-yAsy alloys on the N-rich side have been grown [4], the realized As content had been previously limited to about y ≤ 0.03 [5, 6]. An As content of y ≥ 0.07 is, however, considered necessary for the lasing wavelength of 650 nm that meets requirements for DVD applications. Moreover, the band gap energy of metastable GaNAs within the immiscible region has not been experimentally confirmed. In this report, we denote GaNAs on the N-rich side as ‘GaNAs’ and GaAsN on the As-rich side as ‘GaAsN’ for simplicity. The single-phase GaN1-yAsy alloys with an As content over the *
On leave from Photonic and Wireless Devices Research Laboratories, NEC Corporation, Otsu-shi, Shiga 520-0833, Japan
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range of 0 < y ≤ 0.067 were successfully grown. We report here the detailed growth and properties of these alloys. The optical gap energy for the GaNAs alloy was obtained from optical absorption measurements and its compositional dependence was determined. EXPERIMENTS GaNAs layers were grown to a thickness of 0.25-1 µm on GaN layers on sapphire substrates by low-pressure (76 Torr) metalorganic vapor
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