Abstract
We establish the relationships between growth conditions, strain state, optical and structural properties of nonpolar m-plane (101¯0) InGaN with indium composition up to 39% grown by plasma-assisted molecular beam epitaxy. We find that indium mole fraction as a function of growth temperature can be explained by an Arrhenius dependence of InN decomposition only for high temperature and low indium composition InGaN films. For the samples following the Arrhenius behavior, we estimate the effective activation energy for InN thermal decomposition in m-plane InGaN to be about 1 eV. This value is approximately a factor of two smaller than that reported for c-plane InGaN films. At low growth temperatures, InGaN layers show less efficient indium incorporation than predicted by Arrhenius behavior. We attribute the lower than expected indium composition at low temperatures to the strain-induced compositional pulling effect. We demonstrate that at 540 °C, the increase in the InGaN layer thickness leads to a preferential strain relaxation along the a-direction and an increase in the indium composition. For the indium mole fraction up to x ∼ 0.16, 30-nm-thick m-plane InGaN layers can be coherently grown on GaN with smooth morphology and pronounced low-temperature photoluminescence indicating that the material quality is suitable for device applications.
Highlights
The optical and electronic properties of III-nitride heterostructures that revolutionized the solid state lighting industry make them promising materials for applications in integrated photonic circuits, passive optical devices, and quantum photonic elements.1–3 In nitride-based emitters, detectors, and waveguides, InGaN layers play a critical role allowing bandgap tuning through the change of indium composition
We find that indium mole fraction as a function of growth temperature can be explained by an Arrhenius dependence of InN decomposition only for high temperature and low indium composition InGaN films
We study the impact of growth conditions and strain state on the structural and optical properties of InGaN films grown by plasma-assisted molecular beam epitaxy (PAMBE) on nonpolar (101 ̄0) GaN in the temperature range 450–635 ○C
Summary
The optical and electronic properties of III-nitride heterostructures that revolutionized the solid state lighting industry make them promising materials for applications in integrated photonic circuits, passive optical devices, and quantum photonic elements. In nitride-based emitters, detectors, and waveguides, InGaN layers play a critical role allowing bandgap tuning through the change of indium composition. Polar c-plane GaN surfaces are typically cation stabilized having only Ga species on top of the surface layer In this case, the adatom surface interaction is dominated by metallic Ga-Ga bonds resulting in low and isotropic diffusion barriers.. The low indium incorporation efficiency requires a lower growth temperature for a given indium composition that typically leads to the degradation of epitaxial layers due to the reduced surface adatom mobility. The studies of nonpolar InGaN layers grown by PAMBE were previously limited to high growth temperatures and low indium compositions
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