Influence of substrate doping and point defects on Al and Ga interdiffusion in AlSb/GaSb superlattice structures

Abstract

Positron annihilation spectroscopy has been used to investigate the role of vacancies in the interdiffusion of Al and Ga in AlSb/GaSb superlattices. The samples were grown by metalorganic vapor-phase epitaxy on undoped and Te doped GaSb and consisted of ten periods of GaSb quantum wells (thickness 13 nm) and AlSb barriers (thickness 2–3 nm) and an approximately 50 nm thick capping layer of GaSb. The superlattices were annealed at 908 K for up to 250 s, resulting in interdiffusion of Al and Ga between well and barrier. A secondary ion mass spectrometry study showed that the Te dopant diffused from the substrate through the superlattice structure in the annealing process. In the positron annihilation study we observe that the vacancy concentration clearly decreases with annealing for the samples grown on undoped substrates, whereas the samples grown on Te doped substrates show a different annealing behavior.

Band offsets at zincblende-wurtzite GaAs nanowire sidewall surfaces

“…Even though these shifts are commonly small, they strongly alter the dopant and defect incorporation 1,2 and also the diffusion processes at surfaces or across interfaces. [3][4][5][6] Such shifts in the Fermi level pinning cause even more pronounced modifications of the material properties at the nanoscale. Replacing donor by acceptor impurities in InP nanowires (NWs) redshifts the NW optical emission due to different band bending at the NW surface.…”

Open volume defects in ultra-thin TiO2 layers embedded in VMCO-like samples studied with positron annihilation spectroscopy

“…7 In a similar type of study point defect influence on Al and Ga interdiffusion in AlSb/GaSb superlattice structures, where the well thickness was 13 nm and barriers 2 -3 nm. 8 However, in both of these studies the total sample structure was over 100 nm, making the interpretation of the results more straightforward. In an investigation on point defects in HfO 2 thin films of thicknesses of 10 − 100 nm, Alemany et al found, by applying PAS, higher defect concentrations in atomic layer deposition (ALD) HfO 2 /Si layers than in physical vapor deposition (PVD) layers.…”