High-index-contrast ridge waveguide lasers fabricated via oxygen-enhanced wet thermal oxidation

Di Liang; Jusong Wang; Douglas C. Hall; Gregory M. Peake; Quesnell Hartmann

doi:10.1117/12.647124

22 February 2006 High-index-contrast ridge waveguide lasers fabricated via oxygen-enhanced wet thermal oxidation

Di Liang, Jusong Wang, Douglas C. Hall, Gregory M. Peake, Quesnell Hartmann

Proceedings Volume 6133, Novel In-Plane Semiconductor Lasers V; 613312 (2006) https://doi.org/10.1117/12.647124
Event: Integrated Optoelectronic Devices 2006, 2006, San Jose, California, United States

Abstract

A simple, novel self-aligned deep etch plus wet thermal oxidization process is demonstrated which enables high-index-contrast (HIC) ridge waveguide (RWG) lasers fabricated in a high-efficiency, high-power AlGaAs/InAlGaAs/GaAs graded-index separate confinement heterostructure to operate with a curved half-ring resonator geometry having a bend radius as low as 10 μm. A wet thermal oxidation process modified through addition of <1% O₂ to the N₂ carrier gas is shown to smooth the sidewall roughness of etched AlGaAs ridge structures 10-100 fold as the oxidation front progresses inward. The reduction of propagation scattering loss due to the reduced sidewall roughness is examined. The thermal oxide grown on the deeply-etched RWG sidewalls and base also provides electrical isolation from the contact metallization, resulting in a simplified, self-aligned process, and yields a RWG structure which effectively prevents current spreading. The thermal oxide appears to be of sufficiently high quality to passivate the etched active region surface based on a comparative analysis of straight RWG lasers of varying stripe widths (w=5 to 150 μm) passivated with native-oxide vs. PECVD-deposited SiO₂. For example, at w<15 μm, the SiO₂-insulated devices have ~2X higher threshold current densities than the native-oxide devices for comparable bar lengths. The resulting high lateral optical confinement factor at the semiconductor/oxide interface (Δn=1.69) significantly enhances the laser gain and efficiency. A native-oxide-defined straight laser (w=7 μm, L= 452 μm) operates cw (300 K, unbonded, p-side up) with a threshold current of I_th=21.5 mA (J_th=679.5 A/cm²) and slope efficiency of 1.19 A/W (differential quantum efficiency = 78%) at a wavelength of ~813 nm.

Citation Download Citation

Di Liang, Jusong Wang, Douglas C. Hall, Gregory M. Peake, and Quesnell Hartmann "High-index-contrast ridge waveguide lasers fabricated via oxygen-enhanced wet thermal oxidation", Proc. SPIE 6133, Novel In-Plane Semiconductor Lasers V, 613312 (22 February 2006); https://doi.org/10.1117/12.647124

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