Effect of Growth Temperature on InP QD Lasers
ABSTRACT We describe the effect of growth temperature on the optical absorption, gain, and threshold current density of 730-nm emitting, metal-organic vapor phase epitaxy (MOVPE) grown, InP-AlGaInP quantum-dot lasers. Decreasing the growth temperature from 750??C to 690??C leads to an increase in ground state absorption, while sufficient optical gain and low 300 K threshold current density is obtained in the growth temperature window between 710??C and 730??C . Wider (16 nm compared to 8 nm) interlayer barriers lead to lower threshold current density with 300 K values as low as 165 Acm-2 for 2-mm-long lasers with uncoated facets.
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ABSTRACT: We study self-assembled InP quantum dot (QD) laser structures grown at two temperatures (690°C and 730 °C) each with three different quantities of deposited quantum dot material (2, 2.5, and 3 mono-layers). The absorption spectra of these structures show features associated with the QD distributions and the magnitude of the absorption increases for samples where more material is deposited and for lower growth temperature. The 690°C growth temperature structures exhibit nonradiative recombination and internal optical mode loss that increase with the quantity of material deposited; we suggest that the laser performance is limited by the presence of defects. The higher growth temperature samples have lower threshold current density and are limited by gain saturation. For these samples and for 2-mm long lasers with uncoated facets, the threshold current density is as low as 150 A cm-2, emitting in the wavelength range around 730 nm.IEEE Journal of Quantum Electronics 04/2013; 49(4):389-394. · 2.11 Impact Factor
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ABSTRACT: Optical absorption spectra have been measured by the segmented contact method on InP quantum-dot (QD) laser structuresfordifferentquantitiesofdepositedmaterial,equivalent to 2, 2.5, and 3 mono-layers, and growth temperatures of 690 C and 730 C. The spectra suggest inhomogeneous distributions of "large" and "small" groups of dots and a group of "very large" dots in structures grown at 690 C. The absorption peak energies do not change significantly with the amount of deposited material so we interpret changes in the magnitude of absorption as being due to changes in the density of dots. Using calculated values for the optical cross sections, we have estimated the variation of the number of dots in each group with monolayers of deposited material. The structures grown at 690 C are unusual in that the density of small dots decreases with increasing material deposited whereas the density of very large dots increases superlinearly, suggesting the small dots agglomerate to form the "very large" dots, which may in fact be due to quantum mechanical coupling of closely spaced small dots.IEEE Photonics Technology Letters 01/2011; 23(16):1169-1171. · 2.04 Impact Factor
Conference Paper: Dual-λ InP/AlGaInP quantum dot laser[Show abstract] [Hide abstract]
ABSTRACT: By optimizing the inhomogeneous properties of a QD structure we have created a monolithic dual-wavelength laser, sourcing spatially coherent emission between 650 and 730 nm, with independent control of the light output at each wavelength.Semiconductor Laser Conference (ISLC), 2012 23rd IEEE International; 01/2012