High-Performance Zn-Diffusion 850-nm Vertical-Cavity Surface-Emitting Lasers With Strained InAlGaAs Multiple Quantum Wells

We demonstrate a high-performance Zn-diffusion 850-nm vertical-cavity surface-emitting laser (VCSEL). By the use of strained InAlGaAs/AlGaAs multiple quantum wells for the active region, our structure can have a much higher maximum output power, higher differential quantum efficiency (DQE), and larger modulation current efficiency (D-factor) than those of non-strained control GaAs/AlGaAs VCSELs. Two different Zn-diffusion depths were adopted in our devices with the same single-oxide current-confined aperture (~6 μm) to further optimize the static and dynamic performance, respectively. The device with a deep Zn-diffusion depth (~1.2 μm) shows an optimized static performance, which includes a low threshold current (0.8 mA), high DQE (90% at ~1.2 mA), and a maximum output power as high as 9.7 mW. On the other hand, the device with a shallow Zn-diffusion depth (<; 0.6 μm) demonstrates good dynamic performance and exhibits a large D-factor (9.5 GHz/mA^1/2), high maximum data rate (32 Gbit/s error-free) performance, and very-high data-rate/power-dissipation ratio (5.25 Gbit/s/mW) under an extremely small driving voltage (V_pp: 0.25 V).