Red light emitting injection lasers with vertically-aligned InP/GaInP quantum dots

In this paper, we demonstrate the first injection lasers, using threefold-s tacked vertically-aligned InP/CaInP quantum dots (QD's) as thr active mediu m. The lasers emit in the visible part of the spectrum (690-710 nm) with a threshold current density (j(th)) of 172 A/cm(2) at 90 K, increasing with t emperature up to j(th) = 685 A/cm(2) at 210K. 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 r ise in j(th) is accompanied by a decrease of the integrated photoluminescen ce (PL) intensity, indicating that nonradiative recombination of carriers p lays a significant role with increasing temperature. We assume thermal evap oration of carriers out of the dots and into the wetting layer (WL), where they recombine nonradiatively, to be the process responsible for the increa se in j(th).