Artifact-free secondary ion mass spectrometry profiling of a full vertical cavity surface emitting laser structure

Abstract

The optimization of the structure of vertical-cavity surface-emitting lasers (VCSELs) is required to produce more efficient devices. The secondary ion mass spectrometry (SIMS) technique can provide information about the structure and the distribution of dopants and contaminants. However, VCSELs are relatively thick, contain hundreds of layers with varying compositions, and consist of very thin layers. Classical SIMS is prone to artifacts which decreases the quality of the results. In this work, modifications of the SIMS measurement procedures are presented: high incident angle bombardment reduces the mixing effect; optimization of the extraction parameters increases the signal-to-noise ratio from 2.1 to 24.3 dB; Ion polishing and beam service preserves the quality of the measurement. Due to impact energy modulations quantum wells and barriers are registered as box-shaped features. The raw data is free of artifacts and reflects the realistic distribution of elements. Such accuracy may prove invaluable for further optimization of VCSELs.