Red Light Emitting Injection Lasers with Vertically-Aligned InP/GaInP Quantum Dots

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In this paper, we demonstrate the first injection lasers, using threefold-stacked vertically-aligned InP/GaInP quantum dots (QD's) as the active medium. The lasers emit in the visible part of the spectrum (690-710nm) with a threshold current density (j_<th>) of 172 A/cm^2 at 90 K, increasing with temperature up to j_<th>=685 A/cm^2 at 210 K. We identify the lasing being due to QD ground state transitions. The temperature dependence of j_<th> is investigated in detail. At low temperatures, the threshold current density is almost independent of temperature while, towards higher temperatures, a thermally activated increase is found, strongly depending on QD size. The rise in j_<th> is accompanied by a decrease of the integrated photoluminescence (PL) intensity, indicating that nonradiative recombination of carriers plays a significant role with increasing temperature. We assume thermal evaporation of carriers out of the dots and into the wetting layer (WL), where they recombine nonradiatively, to be the process responsible for the increase in j_<th>.
社団法人応用物理学会の論文
1999-01-30