REDSHIFTING AND BROADENING OF QUANTUM-WELL INFRARED PHOTODETECTORS RESPONSE VIA IMPURITY-FREE VACANCY DISORDERING

The partial intermixing of the well and barrier materials offers uniqu e opportunities to shift locally the bandgap of quantum-well (QW) stru ctures. We have demonstrated red-shifting and broadening of the wavele ngth responses of bound-to-continuum GaAs and InP based quantum-well i nfrared photodetectors (QWIP's) after growth via impurity-free vacancy disordering (IFVD). A comprehensive set of experiments is conducted o n QWIP's fabricated from both as-grown and multiple-quantum-web (MQW) structures, Compared to the as-grown detector, the peak spectral respo nses of the disordered detectors were shifted to longer wavelengths. T he peak absolute response of the disordered GaAs based QWIP is lower b y almost a Factor of four, However, the responsivity characteristics o f the disordered InP based QWIP show no major degradation. In general, with the spectral broadening taken into account, the overall performa nce of the disordered QWIP's has not dropped significantly. Thus, the postgrowth control of the QW composition profiles by impurity-free vac ancy disordering offers unique opportunities to fine tune various aspe cts of a photodetector's response. Theoretical calculations of the abs orption coefficient spectrum are in excellent agreement with the exper imental data.