QUANTUM DOT SEMICONDUCTOR LASERS

Abstract

The formation of coherently strained islands during the growth of strained heterostructures has been exploited to form an array of quantum dots. The shape and size of the islands vary with growth parameters, but exhibit the electronic properties of zero-dimensional systems. One or multiple, vertically coupled, layers of such quantum dots can form the gain region of a separately confined heterostructure (SCH) laser. The properties of such InGaAs/GaAs self-organized quantum dot lasers are described here. The lasers exhibit temperature independent operation up to 100 K and beyond. Typical threshold currents of 200 μm long room temperature lasers vary from 6 to 20 mA. The small-signal modulation bandwidths of ridge waveguide lasers are 5–7.5 GHz at 300 K and increased to >20 GHz at 80 K. We believe that electron-hole scattering intrinsically limits the high-speed performance of these devices, in spite of differential gains as high as ~ 7× 10-14 cm2 at room temperature. Wavelength switching is demonstrated in these devices and preliminary results on long-wavelengths intersubband quantum dot light emitters are also presented.