Improved performance of 10-μm-thick GaAs/AlGaAs vertical-cavity surface-emitting lasers

A 10-μm-thick GaAs/AlGaAs vertical-cavity surface-emitting laser (VCSEL) was fabricated by lifting off GaAs/AlGaAs epitaxial layers from the GaAs substrate to achieve high-density optoelectronic (OE) integration. It was found that the thin-film VCSEL array with a length of 0.25 to 3.0 mm warped due to internal stress in the film itself. The shift created by warping reached 100 μm, and this warping was analyzed with a curved cantilever model with a uniform internal stress of 10⁷ to 10⁹ N/m². To fabricate a thin-film VCSEL array simultaneously on a mount, a diced chip with a thickness of 130 μm was solder bonded onto a glass mount first, followed by lifting off epitaxial layers containing GaAs/AlGaAs VCSELs from the GaAs substrate. Current-voltage-light output characteristics as well as light-emission spectra for thin-film VCSELs were measured and compared at temperatures between 25°C and 75°C. It was found that the dependence of the device characteristics of thin-film VCSELs on temperature was similar to that of VCSELs with a GaAs substrate. The light output of thin-film VCSELs was measured for 1000 h during continuous operation at 25°C and 50°C. About a 20% decrease in optical output in devices without resin mold and no degradation in devices buried in resin mold were observed. Device degradation might be attributable to the internal stress of 10⁷ N/m² and film warp of 0.5-1.0 μm. The thin-film devices buried in resin mold had no changes in laser threshold current before or after 1000 h of continuous operation.