Redshifting and broadening of quantum-well infrared photodetector'sresponse via impurity-free vacancy disordering

摘要

The partial intermixing of the well and barrier materials offersnunique opportunities to shift locally the bandgap of quantum-well (QW)nstructures. We have demonstrated redshifting and broadening of thenwavelength responses of bound-to-continuum GaAs and InP basednquantum-well infrared photodetectors (QWIP's) after growth vianimpurity-free vacancy disordering (IFVD). A comprehensive set ofnexperiments is conducted on QWIP's fabricated from both as-grown andnmultiple-quantum-well (MQW) structures. Compared to the as-grownndetector, the peak spectral responses of the disordered detectors werenshifted to longer wavelengths. The peak absolute response of thendisordered GaAs based QWIP is lower by almost a factor of four. However,nthe responsivity characteristics of the disordered InP based QWIP shownno major degradation. In general, with the spectral broadening takenninto account, the overall performance of the disordered QWIP's has notndropped significantly. Thus, the postgrowth control of the QWncomposition profiles by impurity-free vacancy disordering offers uniquenopportunities to fine tune various aspects of a photodetector'snresponse. Theoretical calculations of the absorption coefficientnspectrum are in excellent agreement with the experimental data