Abstract
Picosecond ultrasonics was used to study the photoelastic properties of zinc-blende (cubic) $c{\text{-Al}}_{x}{\text{Ga}}_{1\ensuremath{-}x}\text{N}$ with $x$ around 0.5. The velocities for longitudinal sound in the alloys were measured using ultrafast UV pump-probe experiments with (AlGa)N membranes. Strong Brillouin oscillations were observed in (AlGa)N films attached to GaAs substrates. These oscillations are due to the dynamical interference of the probe beams reflected from the sample surface and interfaces and a picosecond-duration strain pulse propagating in the alloy layer. Optical and elasto-optical parameters including the complex refractive index and the fundamental band gap of the cubic nitride alloys are determined and compared with the values obtained by ellipsometry.
Highlights
There is a strong demand for efficient deep-UV (
The samples were grown by molecular beam epitaxy (MBE) on semi-insulating (100) GaAs substrates with a c-GaN buffer layer
We have studied zinc-blende (AlGa)N alloys grown by MBE on (001) GaAs substrates and measured the values of complex refractive index and their dependence on Al content and the optical wavelength in the range 250–300 nm
Summary
There is a strong demand for efficient deep-UV (
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