Zirconium nitride/aluminum nitride buffer layers for epitaxial growth of (indium,gallium) nitride on silicon substrates
Abstract
An integral back contact and reflector is demonstrated as an epitaxial template to seed GaN growth on silicon. ZrN was chosen as the ideal candidate material to act as the integral back contact and reflecting layer. ZrN is lattice matched to 14% InN in (In,Ga)N, is a refractory material (Tmelt ∼ 2960°C), and has a high reflectivity in the blue-green portion of the visual spectrum. An additional AlN layer is added to the layer stack to prevent an interfacial reaction between the ZrN and Si as well as to provide electrical isolation of a device. From an industrial standpoint, (In,Ga)N growth on silicon substrates would alleviate the cost constraints of the current LED fabrication technology by allowing for a reduction in costly production steps (laser lift-off, packaging), greater scalability (300mm wafers), reduced wafer cost over sapphire (or SiC), and reduced series resistance by removing current crowding in the final device. The addition of a reflecting layer increases the light emission by reflecting light from the silicon substrate that would otherwise absorb it. This work addresses the issues of substrate processing and film growth from the Si(111) substrate up to (In,Ga)N film growth. A ZrN/AlN bilayer stack is deposited by reactive magnetron sputtering to buffer (In,Ga)N growth on Si(111). The addition of the AlN layer was found to prevent detrimental chemical reactions at process temperatures (T= ∼1000°C) between the ZrN and Si layers, while improving the epitaxial growth of ZrN. GaN and (In, Ga)N were deposited by organometallic vapor phase epitaxy on these ZrN/AlN substrates and produced films with a ω-rocking curve full width at half maximum (FWHM) value of 1230 arc sec for a 800nm film of c-plane oriented GaN (FWHM about GaN 0002 reflection). Although the aim of this research was initially aimed at providing a growth substrate for templated nanorod growth, it also has implications far beyond that specific application, as the GaN-based device industry continues to grow.
Degree
M.S.M.S.E.
Advisors
Sands, Purdue University.
Subject Area
Materials science
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