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

Abstract

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 4µm thick metallic mask made mainly of gold which also served as contact layer, and 640keV hydrogen implantation to a fluency of 1 × 1015cm−2. We obtained the sheet resistivity RSH of (1.5 ± 0.9) × 109Ω/□. 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 1min annealing at 300℃ and 400℃, while the material was still resistive with RSH above 108Ω/□. Based on our simulated vacancy maps we concluded that the minimum width of the masking structure should be at least 5µm 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 6kA/cm2 at the temperature of 77K. Ultimately, we confirmed the applicability of hydrogen implant isolation for the manufacturing of optical devices.