Pixelless infrared imaging devices based on the integration of an n-type quantum well infrared photodetector with a near-infrared light-emitting diode

This paper presents the recent developments of large area focal plane 'pseudo' arrays for infrared (IR) imaging. The devices (called QWIP-LED) are based on the epitaxial integration of an n-type mid-IR (8 - 10 micrometer in the present study) GaAs/AlGaAs quantum well detector with light emitting diode. The originality of this work is to use n-type quantum wells for large detection responsivity. From these structures, very large area (approximately equals cm 2 ) mesas are processed with V-grooves to couple the mid-IR light with the QW intersubband transitions. The increase of spontaneous emission by the mid-infrared induced photocurrent is detected with a CCD camera in the reflection configuration. As demonstrated earlier on p-type QWIP structures the mid-IR image of a blackbody object is up-converted to a near-IR transformed image with very small distortion.