Vertical Cavity Surface Emitting Laser (VCSEL) and Focussed Ion Beam milling combined with Time of Flight Secondary Ion Mass Spectroscopy (FIB-ToF-SIMS)

VCSELs  (see Brtiney Spear’s take on VCSELs http://britneyspears.ac/physics/vcsels/vcsels.htm )are components in the 3D face recognition system used in the later versions of the iPhone  – the VCSELs generate the structured light required to obtain the 3D information from a scene see https://appleinsider.com/articles/18/03/08/apple-vcsel-supplier-suggests-truedepth-coming-to-multiple-iphones-this-fall. They are also used in miniature atomic clocks https://www.photonics.com/Articles/VCSEL-driven_Atomic_Clock_Available_to_Consumers/a46948

The VCSELs include an electrically insulating oxide layer that is used to channel the current in the device.  Fabricating the oxide layer is an important part of the VCSEL manufacturing processes and by using a nanoanalysis technique called FIB-ToF-SIMS the atomic species in the device can be 3D mapped with a resolution down to a few nanometers. At the John De Laeter centre of Curtin University,  we used FIB-ToF-SIMS to analysis the atomic species in a VCSEL manufactured by Compound Semiconductor Technologies.  With FIB-ToF-SIMS we can precisely map out the oxide layer in the VCSEL and determine if it is up to specifications.

When we map out the atomic species of interest in even a small volume we end up with a lot of data – in the movie shown below we show the Gallium, Aluminium and Oxygen atoms in cube volume device 2x2x2 microns – of particular interest is the lower Oxygen atoms -shown in red  in the Aluminium oxide layer – the oxide layer on top is a SiO2 protection layer – not really that important for device operation.

Enjoy the movie:-