Dresden 2006 – scientific programme

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HL: Halbleiterphysik

HL 56: Quantum dots and wires: Preparation and characterization III

HL 56.4: Talk

Friday, March 31, 2006, 11:45–12:00, POT 51

Stacking of InGaAs/GaAs-based quantum dots for long-wavelength laser diodes — •Tim David Germann, André Strittmatter, Thorsten Kettler, Kristijan Posilovic, and Dieter Bimberg — Institute of Solid State Physics, Sekr. PN 5-2, Hardenbergstr. 36, Technical University of Berlin, D-10623 Berlin, Germany

Currently, only a few reports exist on quantum dot (QD) based laser diodes with emission wavelengths beyond 1240 nm grown by MOCVD on GaAs(100) substrates. Stacking of several QD planes is generally proposed in order to increase the gain at the target wavelength. However, the stacking of QD planes for long-wavelength emission around 1300 nm is not much investigated with respect to the chosen material combination. For example, an In_0.65Ga_0.35As QD layer overgrown by an In_0.15Ga_0.85As layer shows photoluminescence emission around 1310 nm with comparable intensity to a similar QD layer overgrown by an In_0.08Ga_0.92As layer which peaks at 1250 nm. In contrast, upon stacking of the In_0.65Ga_0.35As/In_0.15Ga_0.85As combination the photoluminescence intensity starts to deteriorate already when the third QD plane is deposited, while the latter combination could be stacked up to the fifth QD plane without degradation. Furthermore, using an In_0.65Ga_0.35As-QD/In_0.13Ga_0.85As-QW combination for 1290 nm emission only a triple stack could be grown without degradation. Presently, we realized QD laser diodes at a wavelength of 1246 nm with ultra-low threshold current densities of 66 A cm⁻², transparency current densities as low as 10 A cm⁻² per QD plane, and high internal quantum efficiencies of 94 %.