Abstract
In this paper, we present a parametric study of high performance microdisk lasers at 1.55 μm telecom wavelength, monolithically grown on on-axis (001) Si substrates incorporating quantum dots (QDs) as gain elements. In the optimized structure, seven layers of QDs were adopted to provide a high gain as well as a suppressed inhomogeneous broadening. The same laser structure employing quantum wells (QWs) on Si was concurrently evaluated, showing a higher threshold and more dispersive quantum efficiency than the QDs. Finally, a statistical comparison of these Si-based QD microdisk lasers with those grown on InP native substrates was conducted, revealing somewhat higher thresholds but of the same order. The monolithically grown QD microlasers on Si also demonstrated excellent temperature stability, with a record high characteristic temperature of 277 K. This work thus offers helpful insight towards the optimization of reliable Si-based QD lasers at 1550 nm.
Highlights
With high efficiency and high speed operation due to their high quality factor Q and small volume V, microdisk lasers (MDLs) emitting at near infrared wavelengths are excellent candidates for on-chip integration
Fundamental challenges including high density (109-1010 cm−2) of threading dislocations (TDs) and planar defects associated with material mismatch and different polarities of III-V and Si are impeding the advancement of heteroepitaxy
We found that equipping more stacks of quantum dots (QDs) to achieve a higher gain overcoming the loss of higher order modes in the whispering-gallery modes (WGMs) cavity is essential
Summary
With high efficiency and high speed operation due to their high quality factor Q and small volume V, microdisk lasers (MDLs) emitting at near infrared wavelengths are excellent candidates for on-chip integration. The monolithic growth method to integrate III-V lasers on Si has gained renewed interest and been extensively investigated in recent years by virtue of the potential low-cost, high-yield, and large-scale integration of complex optoelectronic circuits [5]. Fundamental challenges including high density (109-1010 cm−2) of threading dislocations (TDs) and planar defects associated with material mismatch and different polarities of III-V and Si are impeding the advancement of heteroepitaxy. The longest emission wavelength reported for such lasers is 1.3 μm, utilizing InAs/GaAs QDs, and for the important C-band lasers at 1.55 μm, progress is hindered by two factors: first, difficulties in achieving uniform and dense InAs QDs on InP due to the small lattice mismatch (only ~3.2%) and complex strain distribution [11], and second, challenges in InP-on-Si buffer growth with a quite large lattice mismatch of ~8% [7]
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