Electrical isolation of GaAs and AlGaAs/GaAs Quantum Cascade Lasers by deep hydrogen implantation

Ion implantation can be applied to form the electrical isolation in AlGaAs/GaAs Quantum Cascade Laser (QCL) instead of mesa etching. In this paper, we present in detail the designing of hydrogen implant isolation scheme, alongside with its verification and study of thermal stability by structural and electrical characterization techniques. Our scheme employed 4 µm thick metallic mask made mainly of gold which also served as contact layer, and 640 keV hydrogen implantation to a fluency of 1 × 1015 cm−2. We obtained the sheet resistivity RSH of (1.5 ± 0.9) × 109 Ω/□. The critical temperature for the hydrogen implant isolation fabrication of the AlGaAs/GaAs QCL was determined to be 310 ℃. Defect density dropped to residual levels after 1 min annealing at 300 ℃ and 400 ℃, while the material was still resistive with RSH above 108 Ω/□. Based on our simulated vacancy maps we concluded that the minimum width of the masking structure should be at least 5 µm to avoid the effects of lateral isolation for the given implantation conditions. The QCL device fabricated with this isolation scheme operated with threshold current densities of 6 kA/cm2 at the temperature of 77 K. Ultimately, we confirmed the applicability of hydrogen implant isolation for the manufacturing of optical devices.