COMPOSITION FLUCTUATIONS IN III-V SEMICONDUCTORS

Electron microscopy studies have previously revealed the presence of fine scale (10nm) variations of contrast within III-V compound semiconductor epilayers. Using a pulsed laser atom probe it has been possible to study the microchemistry of these layers at very high resolution. This study has shown that in epilayers of GaInAs, AlInAs and GaAlInAs there are variations of up to 10% in composition. In the GaAlInAs system the epilayer is seen to cluster towards small regions of GaInAs and GaAlAs. Preliminary experiments using a position-sensitive atom probe have confirmed that the composition variations can be further quantified using three dimensional microanalysis techniques