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 cm 2 V-1 s-1 and a low sheet resistance, R ∼ 210 Ω/.