QWIP with electron launcher for reducing dielectric relaxation effect in low background conditions
View Patent ↗A QWIP structure is disclosed that includes a graded emitter barrier and can further be configured with a blocked superlattice miniband. The graded emitter barrier effectively operates to launch dark electrons into the active quantum well region, thereby improving responsivity. A graded collector barrier may also be included for reverse bias applications. The configuration operates to eliminate or otherwise reduce image artifacts or persistence associated with dielectric relaxation effect in low-background applications.
1. A quantum well infrared photodetector (QWIP) device comprising:
an emitter contact layer;
a stack including a superlattice structure of quantum wells, each well sandwiched between thin barrier layers that allow tunneling between the wells, thereby enabling rapid refilling of depleted wells and neutralization of space charge buildup; and
an electron launcher configured with a plurality of steps to enable dark electrons to move rapidly from the emitter contact layer into the stack, thereby reducing dielectric relaxation effect.
2. The device of claim 1 wherein a first barrier in the stack is defined by a particular semiconductor material make-up, and each step of the electron launcher adds about 25% or less of that first barrier's make-up.
3. The device of claim 1 wherein the device is configured as an indirect-gap type structure, and the quantum wells are GaAs and the barriers are AlGaAs.
4. The device of claim 1 wherein the device is configured as a strained type structure, and the quantum wells are InGaAs, and the barriers are AlGaAs.
5. The device of claim 1 wherein the quantum wells have a width of about 60 Å to 90 Å, and the barriers have a thickness of about 45 Å to 65 Å.
6. The device of claim 1 wherein the device further includes a collector contact layer that is proximate to a last barrier included in the stack.
7. The device of claim 6 wherein the device further includes a blocking layer between the stack and the collector contact layer for suppressing tunneling current from the quantum wells.