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This paper reports on GaN/AlN light-emitting devices relying on intersubband transitions. All samples have been grown by molecular beam epitaxy. We first present a systematic investigation of single or coupled GaN/AlN quantum wells grown by MBE. We then present the recent observation of strong ISB resonant enhancement of the second-harmonic generation of 1μm radiation. We finally report on the first observation of ISB luminescence in GaN QWs, which opens new prospects for the realization of nitride unipolar lasers based on current injection or optical pumping. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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We report the demonstration of intersubband modulators operating at telecommunication wavelengths at room temperature based on GaN/AlN quantum wells. We first investigate electro-optical modulators making use of electron tunneling in coupled quantum wells. Electro-absorption modulation with opposite sign induced by the electron tunneling between the reservoir and active quantum wells is observed at λ 1.3–1.6 µm and λ 2.2 µm. We show that by reducing the mesa size down to 15 × 15 µm2, optical modulation bandwidth as large as 3 GHz can be obtained. We then investigate waveguide intersubband modulators relying on the depletion of the ground electronic state of a 3 quantum well active region. Modulation depths as large as 14 dB in the wavelength range of 1.2–1.6 µm are obtained under –9 V/7 V voltage swing. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)