Current status of AlInN layers lattice-matched to GaN for photonics and electronics

Abstract

We report on the current properties of Al1−xInxN (x ≈ 0.18) layers lattice-matched (LM) to GaN and their specific use to realize nearly strain-free structures for photonic and electronic applications. Following a literature survey of the general properties of AlInN layers, structural and optical properties of thin state-of-the-art AlInN layers LM to GaN are described showing that despite improved structural properties these layers are still characterized by a typical background donor concentration of (1–5) × 1018 cm−3 and a large Stokes shift (∼800 meV) between luminescence and absorption edge. The use of these AlInN layers LM to GaN is then exemplified through the properties of GaN/AlInN multiple quantum wells (QWs) suitable for near-infrared intersubband applications. A built-in electric field of 3.64 MV cm−1 solely due to spontaneous polarization is deduced from photoluminescence measurements carried out on strain-free single QW heterostructures, a value in good agreement with that deduced from theoretical calculation. Other potentialities regarding optoelectronics are demonstrated through the successful realization of crack-free highly reflective AlInN/GaN distributed Bragg reflectors (R > 99%) and high quality factor microcavities (Q > 2800) likely to be of high interest for short wavelength vertical light emitting devices and fundamental studies on the strong coupling regime between excitons and cavity photons. In this respect, room temperature (RT) lasing of a LM AlInN/GaN vertical cavity surface emitting laser under optical pumping is reported. A description of the selective lateral oxidation of AlInN layers for current confinement in nitride-based light emitting devices and the selective chemical etching of oxidized AlInN layers is also given. Finally, the characterization of LM AlInN/GaN heterojunctions will reveal the potential of such a system for the fabrication of high electron mobility transistors through the report of a high two-dimensional electron gas sheet carrier density (ns ∼ 2.6 × 1013 cm−2) combined with a RT mobility μe ∼ 1170 cm2 V−1 s−1 and a low sheet resistance, R ∼ 210 Ω/□.

Stabilization of wurtzite Sc0.4Al0.6N in pseudomorphic epitaxial Sc Al1−N/In Al1−N superlattices

“…These experimental results support mixing enthalpy results for relaxed and differently Previous studies of InyAl1-yN show a tendency for random compositional fluctuations during the early stages of growth, which leads to a wavy surface [32], and may explain the higher degree of roughness observed in our ScxAl1-xN/InyAl1-yN samples that is not present in ScxAl1-xN/AlN. In our previous study of ScxAl1-xN thin films, we demonstrated a correlation between columnar microstructure and good crystalline quality [10], suggesting that the columnar microstructure in the present ScxAl1-xN/InyAl1-yN superlattices also indicates an improved crystalline quality.…”

Comparison of the transport properties of high quality AlGaN/AlN/GaN and AlInN/AlN/GaN two-dimensional electron gas heterostructures

“…Furthermore, of these successful results reported in the literature there are only a few reports in terms of the detailed analysis of the transport characteristics of AlInN-based HEMTs. 5,19 In the present work, we investigated and compared the transport properties of high quality AlGaN/AlN/GaN and AlInN/AlN/GaN heterostructures using temperature dependent Hall effect measurements. Analytical models were applied to the experimental results in order to understand the scattering mechanism that governs the performance of devices in a temperature range of 30-300 K. If the scattering mechanisms that are dominant for high-density 2DEGs can be identified, it will guide the modifications to the growth and/or the layer structure that will be necessary to further improve the conductivity.…”

Standard‐free composition measurements of Alx In1–xN by low‐loss electron energy loss spectroscopy

“…For example, alloying the two binary nitrides InN and AlN results in the ternary compound Al x In 1-x N, with a bandgap that spans from 0.64 eV to 6.2 eV [2,3]. Al x In 1-x N is particularly attractive since it can be grown lattice matched to GaN and AlGaN [4], ensuring stress-free heterostructures with tunable bandgap [5]. Simultaneously, the constant size reductions of III-nitride device structures are accompanied by a need for increased control and understanding of growth and diffusion mechanisms [6,7] along with accurate compositional and structural information.…”