In situ cavity length control of GaN-based vertical-cavity surface-emitting lasers with in situ reflectivity spectra measurements

We developed an in situ cavity length control of GaN-based vertical-cavity surface-emitting lasers (VCSELs) with an in situ reflectivity spectra measurement. Firstly, a temperature dependence of a center wavelength of a 40-pair AlInN/GaN DBR was investigated, resulting in a 23 nm redshift from RT to GaN growth temperature of 1100 °C. Secondly, a periodic oscillation of a reflectivity intensity during the GaN cavity growth on the DBR was clearly observed, providing precise cavity length information. Thirdly, based on both the results, we performed the in situ GaN cavity length control, showing an accuracy within a 0.5% error. We finally demonstrated the in situ cavity length control of an actual GaN-based VCSEL structure containing n-layers, a GaInN active region, and p-layers by selecting different resonance wavelengths along with the corresponding growth temperatures for the layers.