Multicolour infrared detection with In/sub 0.1/Ga/sub 0.9/As/Al/sub 0.33/Ga/sub 0.67/As double and triple-coupled quantum well infrared photodetectors

Two structures, designed to detect two and three infrared colours using coupled quantum wells in the are demonstrated. Both structures were initially grown without contacts on double-sided substrates to facilitate infrared absorption measurements. The 'two-colour' sample shows absorption at 7.4 /spl mu/m and 9.1 /spl mu/m, whereas the 'three-colour' sample shows absorption at 6.25 /spl mu/m, 9.5 /spl mu/m and 12.8 /spl mu/m. To our knowledge this is the first time coupled quantum wells of the same composition have been used to detect multiple colours. Samples were then grown with contact layers to facilitate photoresponse measurements. Current-voltage and black body responsivity measurements are presented for these devices.