Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 9: Semiconductor Laser II

HL 9.5: Talk

Monday, March 26, 2007, 15:45–16:00, H13

High modal gain and low threshold temperature dependence of InGaAlAs quantum dot lasers with increased dot density — •Thomas Schlereth, Christian Schneider, Wolfgang Kaiser, Sven Höfling, and Alfred Forchel — Technische Physik, Physikalisches Institut, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany

The growth, morphology and spectral properties of In_xGa_1−xAs and In_xGa_1−x−yAl_yAs quantum dots (QDs) were studied. The emission wavelength of the QDs can be tuned in a wide range by varying the In and Al content. Furthermore, an increase in Al concentration results in an enhancement of dot density and a decrease of dot size. This phenomenon can be explained by the lower migration ability of Al compared to In.

By adjusting the In and Al content, lasers with different dot species (InGaAs and InGaAlAs), and different dot densities (factor of ∼2.5), yet similar emission wavelengths (∼920 nm) have been realized. Both laser samples exhibit high internal quantum efficiencies and low internal absorptions of 0.83 and ∼2cm⁻¹ for the InGaAs and 0.79 and ∼1 cm⁻¹ for the InGaAlAs sample. The sample containing InGaAlAs QDs, however, shows a factor of ∼1.6 higher modal gain (∼63 cm⁻¹), and a lower threshold current density, which we attribute mainly to the higher dot density. Characteristic temperatures as high as 174 K for the Al-containing QD laser and 144 K for the InGaAs QD laser were found between 15^∘C and 85^∘C.