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Proceedings Paper

High-index-contrast ridge waveguide lasers fabricated via oxygen-enhanced wet thermal oxidation
Author(s): Di Liang; Jusong Wang; Douglas C. Hall; Gregory M. Peake; Quesnell Hartmann
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Paper 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 Ith=21.5 mA (Jth=679.5 A/cm2) and slope efficiency of 1.19 A/W (differential quantum efficiency = 78%) at a wavelength of ~813 nm.

Paper Details

Date Published: 22 February 2006
PDF: 12 pages
Proc. SPIE 6133, Novel In-Plane Semiconductor Lasers V, 613312 (22 February 2006); doi: 10.1117/12.647124
Show Author Affiliations
Di Liang, Univ. of Notre Dame (United States)
Jusong Wang, Univ. of Notre Dame (United States)
Douglas C. Hall, Univ. of Notre Dame (United States)
Gregory M. Peake, Sandia National Lab. (United States)
Quesnell Hartmann, Epiworks, Inc. (United States)

Published in SPIE Proceedings Vol. 6133:
Novel In-Plane Semiconductor Lasers V
Carmen Mermelstein; David P. Bour, Editor(s)

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