Room temperature photovoltaic response of split-off band infrared detectors with a graded barrier

Split-off band detectors have been demonstrated operating at or above room temperatures. However the specific detectivity was somewhat low due to the high dark current. Increasing the barrier height can suppress the dark current at high temperatures but results in a low responsivity due to the capture of carriers in emitters. A difference between the heights of the barriers on the two sides of an emitter provides highly energized carriers injected into the emitter and hence reduces the trapping effects. Three p-GaAs/AlGaAs samples with different Al fractions in the graded barriers are used to test these effects. Due to the graded barrier, the samples have an asymmetric band structure which makes it easier for excited carriers to travel in one direction than in the other. Therefore, photovoltaic operation is possible due to the built-in potential under equilibrium. Preliminary results obtained from these samples will be discussed.