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16 February 2011 The lateral ambipolar diffusion length in quantum dot lasers
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Proceedings Volume 7953, Novel In-Plane Semiconductor Lasers X; 795306 (2011)
Event: SPIE OPTO, 2011, San Francisco, California, United States
Using the segmented contact technique we determine the lateral out-diffusion current in shallow etched quantum dot ridges of different width and by fitting this out-diffusion data we obtain the ambipolar diffusion length as a function of the intrinsic carrier injection level. The measured data reveals two regimes of reduced diffusion that can be explained by a mechanism involving the thermal redistribution of carriers via the wetting layer. In a high performance 5 layer quantum dot structure operated at 350K the diffusion length varies between 0.75 and 1.5 μm as the peak modal gain increases from 5 to 11cm-1. In dot-in-well quantum dot samples fabricated into deep etched ridge lasers we demonstrate the improved performance and reduced ridge-width dependence of threshold current density as compared to quantum well material, which is identical except for the presence of the dots and wetting layer. For example in 6μm wide, 1500 μm long quantum dot ridges at 300K the threshold current density is 41% of that of the corresponding quantum well ridge. Furthermore, at 230K the threshold current density of the 6 μm ridge increases by a factor of 1.1 as compared to similar 20μm wide ridges whereas in quantum well ridge lasers the threshold current density increases by a factor of 3.2 for the same pair of ridge widths. This corresponds to a threefold decrease in the ridge width dependence of QD ridge lasers compared to QW based lasers. This different dependence on ridge width corresponds to the different lateral diffusion characteristics of the quantum well and self assembled quantum dot material.
© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
A. Sobiesierski, D. Naidu, and P. M. Smowton "The lateral ambipolar diffusion length in quantum dot lasers", Proc. SPIE 7953, Novel In-Plane Semiconductor Lasers X, 795306 (16 February 2011);

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