Epitaxial Lateral Overgrowth of GaN with Chloride-Based Growth Chemistries in Both Hydride and Metalorganic Vapor Phase
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Department of Chemical Engineering, University of Wisconsin, Madison, WI 53706 Department of Physics, Nanjing University, Nanjing 210093, China c Aldrich Chemical, Milwaukee, WI b
Cite this article as: MRS Internet J. Nitride Semicond. Res. 4S1, G4.7 (1999) ABSTRACT Epitaxial lateral overgrowth (ELO) of GaN on SiO2-masked (0001) GaN substrates has been investigated by using chloride-based growth chemistries via hydride vapor phase epitaxy (HVPE) and metal organic vapor phase epitaxy (MOVPE). Diethyl gallium chloride, (C2H5)2GaCl, was used in as the MOVPE Ga precursor. The lateral and vertical growth rates as well as the overgrowth morphology of ELO GaN structures are dependent on growth temperature, V/III ratio and the in-plane orientation of the mask opening. A high growth temperature and low V/III ratio increase the lateral growth rate and produce ELO structures with a planar surface to the GaN prisms. High-quality coalesced and planar ELO GaN has been fabricated by both growth chemistries. The use of the diethyl gallium chloride source allows for the benefits of HVPE growth to be realized within the MOVPE growth environment. INTRODUCTION GaN and related compounds are being developed for short wavelength light-emitting devices, such as laser (LD) and light-emitting diodes (LED), in addition to high temperature and high power electronics. GaN-based LEDs and LDs have been successfully developed and are being commercialized. Several factors impede the further development of GaN devices. A principal difficulty is the high density of dislocations within the GaN epilayers, which can be as high as 108-1010/cm2 [1]. Recently, epitaxial lateral overgrowth (ELO) has been demonstrated to effectively reduce the dislocation density in the GaN epilayers within the lateral overgrown regions [2]. Long-lifetime GaN LDs fabricated on ELO-grown materials has been reported [3]. Most reports on GaN ELO have used the metalorganic vapor phase epitaxy (MOVPE) growth technique [4,5]. Hydride vapor phase epitaxy (HVPE) is also a very attractive technique for GaN ELO. HVPE utilizes GaCl generated in situ through the reaction of liquid Ga with HCl. HVPE offers a high growth rate and high material quality for GaN growth [6,7]. The typical growth rate can be as high as 100-200 µm/hr. The halide process has been shown to offer a higher lateral-tovertical growth rate ratio [8] than MOVPE materials, which is critical for ELO. GaN produced by the HVPE technique does result in a greatly reduced intensity of the defect-based luminescence referred to as the yellow band (YL) when compared to the TMG-based MOVPE materials. This has been attributed to the lack of carbon in the HVPE growth system but is present in the growth sources used in MOVPE-growth systems. Intentional carbon introduction Downloaded from https://www.cambridge.org/core. IP address: 188.68.0.128, on 25 Jan 2019 at 07:55:52, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/S1092578300002908
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