Terahertz quantum well infrared detectors

We report on recent measurements on GaAs/AlGaAs THz quantum well infrared photodetectors (QWIPs), investigating linewidth broadening as function of doping level. Structures with 3% and 2% Al content in the barrier were grown using molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD), respectively. Linewidth widening with increasing doping of the GaAs quantum well could be observed in the detection spectra. The observed shift of peak detection wavelength for different well dopings fits with values obtained from wavefunction calculations, taking into account many-particle effects, namely exchange and correlation energies and the effect of depolarization on the absorption. In addition, activation energies extracted from dark current measurements as function of device temperature are also in agreement with the calculations.