Experimental Investigation of Hot Carriers in Terahertz Quantum Cascade Lasers

G. Scamarcio a, M.S. Vitiello a and V. Spagnolo b a INFM-CNR Regional Laboratory LIT3, Physics Department, University of Bari, via Amendola 173, 70126 Bari, Italy b INFM-CNR Regional Laboratory LIT3, Physics Department, Politecnico di Bari, Italy

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Received: 26 08 2007;

The nature of the electron distribution and the electron-lattice energy relaxation phenomena in all classes of quantum cascade lasers operating in the THz range, namely, resonant-phonon, bound-to-continuum, and interlaced photon-phonon designs are reviewed. Thermalized hot-electron distributions are found in all cases. However, electronic temperatures of individual conduction subband are strongly influenced by the specific quantum design and the actual electron-lattice energy relaxation channels. A wealth of information was obtained both below and above laser threshold from the analysis of micro-probe band-to-band photoluminescence spectra recorded with a spatial resolution of ≈ 2 μm. The influence of the detailed knowledge of the hot electron distributions on the design of improved THz quantum cascade lasers aiming at high temperature operation will be discussed.

DOI: 10.12693/APhysPolA.113.787 PACS numbers: 42.55.Px, 68.65.Fg