| Infrared detectors and modulators are widely used for both defense and commercial applications. This thesis reports on novel infrared detector and modulator structures which have been grown by molecular beam epitaxy and possess a major advantage over conventional multi-quantum well (MQW) devices in that the normal incidence radiation is absorbed. Chapter 2 focuses on the optical polarization selection rules which forbid normal incidence absorption in direct-gap {dollar}Gamma{dollar}-valley QWs while such transitions are allowed for indirect-gap ellipsoidal-valley QWs. In Chapter 3, the growth techniques and procedure are discussed. The effects of different orientations on the Sb-related materials are studied, indicating that tilted substrate leads to a decrease in native defects and surface morphology. The normal incidence MQW structures are reported in Chapter 4. Furthermore, the fabrication of normal incidence photodetector is investigated. Also the different substrate orientations are discussed because they contribute to the large absorption coefficient as predicted theoretically. In Chapter 5, the double stepped asymmetric AlSb/InAs/Al{dollar}rmsb{lcub}0.4{rcub}Gasb{lcub}0.6{rcub}{dollar}Sb/GaSb MQW modulator is fabricated. The normal incidence modulation is demonstrated utilizing {dollar}Gamma{dollar}-L transitions for the first time. |
