Regensburg 2010 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 64: Quantum Dots and Wires: Optical Properties VI

HL 64.8: Vortrag

Freitag, 26. März 2010, 12:15–12:30, H14

Proposal for a nanowire-based terahertz quantum cascade laser — •Thomas Grange and Peter Vogl — Walter Schottky Institut, Technische Universität München, 85748 Garching, Germany

In spite of many efforts of optimization in the past few years, operation of terahertz quantum cascade laser (THz QCL) is still limited to cryogenic temperature. In THz QCLs, the lasing transition occurs between two subbands which are separated by less than the optical phonon energy. As the temperature increases, electrons gain sufficient in-plane kinetic energy in order to scatter efficiently between subbands by emitting optical phonons, reducing drastically the population inversion. An efficient way to circumvent this limitation is to use a structure in which the lateral motion of electrons is quantized. The use of an array of nanowires seems an appealing solution. In the present work, we calculate the transport and optical gain in nanowire heterostructures. Our calculation is made in the non-equilibrium green function (NEGF) framework. We incorporate scattering mechanisms due to interaction with phonons. Anharmonic interaction between phonons is also taken into account since it leads to scattering between the polaron states formed by electrons interacting with polar optical phonons [1,2]. We propose a structure that yields optical gain up beyond room temperature in the THz range. We highlight the physical differences with usual QCLs based on homogeneous 2-D layers.

[1] T. Grange, R. Ferreira and G. Bastard, Phys. Rev. B 76, 241304(R) (2007).

[2] E. A. Zibik et al., Nature Materials 8, 803 (2009).