Different InAs quantum dot structures grown on InGaAlAs lattice matched to InP were investigated for quantum dot infrared photodetectors. Extremely narrow photocurrent peaks were observed, demonstrating great potential for fine wavelength selection. Structures which can detect radiation beyond 10μm were developed. Polarization dependence measurements showed that the structures have a zero-dimensional character and are suitable for detection of normal incident light. On the other hand, structures containing coupled quantum wells showed a hybrid two-dimensional/zero-dimensional behavior.
Photon-assisted tunneling in a multiple-quantum-well superlattice is enhanced as the photon energy becomes resonant with the first intersubband transition. At resonance the process is characterized by tunneling from real states occupied by photoexcitation. Qualitative differences emerge between photon-assisted tunneling controlled by virtual states, under off-resonance conditions, and photon-assisted tunneling from real states, occupied by photoexcitation when on resonance.
InAs quantum dot structures grown on InGaAlAs have been investigated for midinfrared photodetection. Intraband photocurrent and absorption measurements, together with a full three-dimensional theoretical modeling revealed that a bound-to-bound optical transition, where the final state is about 200meV deep below the conduction band continuum, is responsible for the photogenerated current. The reported results strongly suggest that an Auger process plays a fundamental role in generating the observed intraband photocurrent. Photoluminescence and interband photocurrent spectra of the same structures further support the reached conclusions.
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