A VOLTAGE-CONTROLLED TUNABLE 2-COLOR INFRARED PHOTODETECTOR USING GAAS ALAS/GAALAS AND GAAS/GAALAS STACKED MULTIQUANTUM WELLS/

A voltage-controlled tunable two-color infrared detector with photovol taic (PV) and photoconductive (PC) dual-mode operation at 3-5 mu m and 8-14 mu m using GaAs/AlAs/AlGaAs double barrier quantum wells (DBQWs) and bound-to-continuum GaAs/AlGaAs quantum wells is demonstrated. The photoresponse peak of the photovoltaic GaAs/AlAs/GaAlAs DBQWs is at 5 .3 mu m, and that of the photoconductive GaAs/GaAlAs quantum wells is at 9.0 mu m. When the two-color detector is under a zero bias, the spe ctral response at 5.3 mu m is close to saturate and the peak detectivi ty at 80 K can reach 1.0X10(11) cmHz(1/2)/W, while the spectral photor esponsivity at 9.0 mu m is absolutely zero completely. When the extern al voltage of the two-color detector is changed to 2.0 V, the spectral photoresponsivity at 5.3 mu m becomes zero while the spectral photore sponsivity at 9.0 mu m increases comparable to that at 5.3 mu m under zero bias, and the peak detectivity (9.0 mu m) at 80 K can reach 1.5X1 0(10) cmHz(1/2)/W. Strictly speaking, this is a real bias-controlled t unable two-color infrared photodetector. We have proposed a model base d on the PV and PC dual-mode operation of stacked two-color QWIPs and the effects of tunneling resonance with narrow energy width of photoex cited electrons in DBQWs, which can explain qualitatively the voltage- controlled tunable behavior of the photoresponse of the two-color infr ared photodetector. (C) 1996 American Institute of Physics.