| This thesis describes a novel photodetector geometry, the corrugated quantum well infrared photodetector (C-QWIP), which is designed to couple normal incident radiation into the quantum well structures. The C-QWIP structure is an array of QWIP wires with slant sidewalls, fabricated by etching V-grooves through the detector active region down to the bottom contact. It utilizes total internal reflection at the sidewalls of these QWIP wires to create favorable optical polarization for absorption. We have demonstrated that it has higher coupling efficiency in comparison with the standard 45;We have applied the corrugated coupling scheme to a two-color QWIP narrowly peaked at two wavelength ranges, and tested its ability for remote temperature sensing. High optical coupling efficiency is obtained in both wavelength ranges. By monitoring the ratio of the photocurrent generated simultaneously in each detection window, the temperature of the radiation emitting object can be determined. The agreement between the measured and the preset temperatures indicates that the C-QWIP is capable of precision thermometric measurements. For further performance improvement, we have implemented the corrugated coupling scheme into an infrared hot-electron transistor (IHET) to form a new detector structure. In this corrugated infrared hot-electron transistor (CI-HET), an energy filter is grown next to a standard QWIP for more selective collection of the current. At the same time, corrugated structure is physically fabricated into the detector pixel to increase light absorption in the QWIP. With this combined approach, we are able to increase ;We have developed a multi-layer planarization scheme using polyimide as dielectric material to isolate the exposed active detector regions from the metal contacts. C-QWIPs with and without the incorporation of polyimide are characterized and compared. Experimental results show that there is no observable leakage current as a result of this planarization procedure, and the advantages of the coupling scheme are preserved. |
