Wet oxidation and its influence on high performance five-junction 940 nm VCSELs

The application of high-performance VCSELs is extending from consumer electronics to automotive applications. Wet oxidation is an important technology in the fabrication of VCSELs. In this paper, we studied the wet oxidation process and mechanism in order to accurately control the oxidation aperture and improve the power and the conversion efficiency. Current density distributions of VCSELs with different oxide apertures are simulated based on COMSOL Multiphysics. In the experiment, the output power, conversion efficiency and threshold current of single junction and five-junction 940 nm VCSELs varying with oxide apertures are measured. Five-junction VCSELs exhibit maximum power conversion efficiencies are more than 60% and slope efficiency are more than 5.28W/A with oxide aperture from 9 to 15 μm under room temperature pulse condition (50 µs pulse width, 0.5% duty cycle). In addition, 385-element five-junction VCSEL array exhibits maximum power conversion efficiency of 53.45%. The five-junction VCSELs can be used as the basic laser source for the automotive applications.