Terahertz emission from InGaN LED structures: excitation energy and bias dependence study

Summary form only given. The electro-optic sampling method is used for detecting THz emission from InGaN LED structures excited by a frequency-doubled femtosecond Ti:sapphire laser. The intrinsic layer consists of 5 wells of In/sub 0.15/Ga/sub 0.85/N (2 nm) and 4 barriers of GaN (10 nm). The signal amplitude is strongly dependent on the bias voltage. As the reverse bias goes up, the signal amplitude increases. Oscillations with 8-9 ps periods are observed, which corresponds almost exactly with the total intrinsic layer thickness divided by the sound velocity of the system. A remarkable ringing over several THz cycles is observed. While we do not yet understand the precise origin, it might suggest the involvement of acoustic wave packets traveling within the layer structures.