Infrared photodetectors based on III-V semiconductor quantum wells and dots

In this thesis, the feature of voltage tunable photoresponse of two stack superlattice-coupled quantum well infrared photodetector (QWIP) was studied. The difference of photoresponse in dots, dots-in-a-well, dots-in-a-graded-well quantum dots structure were compared. Based on this comparison, a Broadband InAs/InGaAs/GaAs quantum dots infrared photodetector (QDIP) was designed and fabricated, and its broadband photoresponse was obtained.; Voltage tunable features of superlattice-coupled two stack QWIPs were investigated. Under different bias voltages the devices' photoresponse peak intensity shifted from 6.0 mum to 10.3 mum at T = 7 K. This peak was due to the bound-to-bound transitions from the different stacks.; Dots-in-a-graded-well QDIP was also designed, fabricated and their photoresponses were explored. The photoresponse intensity of the dots in a graded well photodetector was significantly higher than both dots and dots in a well infrared photodetector. A broadband QDIP was obtained by grading the Indium composition from 30% to 0%. The full width at half maxim (FWHM) of the photoresponse was observed at 4.0 mum and it was centered at 6.0 mum.