GaN-based Quantum Cascade Research Articles

Evidence of strong electron-phonon interaction in a GaN-based quantum cascade emitter

Abstract We present a GaN-based quantum-cascade device whose inter-subband emission shows strong electron-phonon interaction. To generate the luminescence, an external electrical field – which partially screened the internal polarization – had to be applied. In low intensity spectra, a pattern of secondary peaks occurs. Each side-peak is separated from its fundamental inter-subband transition by a characteristic phonon energy, which shifts with applied field at the same rate as the main transition. At high intensity, there exists resonance between the 92 meV LO-phonon and the vertical inter-subband transition. A strong electrical field of >1 MV cm−1 reduced via QCSE the transition energy from 230 meV to 80 meV. Additionally, the low active region doping necessitated large operating voltages. Besides the emission of mid-infrared radiation, the elevated voltage generated lots of phonons. At an electrical field of 1.02 MV cm−1, the frequency-shifted inter-subband luminescence became resonant with the LO-phonon. The effects of this resonance will be discussed.

Two-color GaN/AlGaN quantum cascade detector at short infrared wavelengths of 1 and 1.7 μm

A two-color GaN-based quantum cascade detector is demonstrated. This photodetector operates simultaneously at a peak wavelength of 1.7 and 1 μm at room temperature without any external voltage. These peaks correspond, respectively, to the e1e2 and e1e3 intersubband absorption of the active GaN quantum well. The extractor has been designed to allow for efficient transfer of electrons from both the e2 and e3 states to the next period. The 1 μm detected wavelength is the shortest value reported for an intersubband semiconductor based detector.

GaN-based quantum cascade photodetector with 1.5 µm peak detection wavelength

Demonstrated is a GaN/Al(Ga)N quantum cascade detector operating at room temperature with a peak detection wavelength of 1.5 m, which is the shortest value ever reported for such a device in any material system. The 3 dB detection spectral range spans from 1.37 to 1.57 m wavelength. The calibrated peak responsivity for TM-polarised light is measured to be around 15 V/W at room temperature.