Dual Common Planes for Time Multiplexing of Dual-Color QWIPs

With external command commercial single-color readout integrated circuits could be used.

NASA's Jet Propulsion Laboratory, Pasadena, California

A propos improved process of externally controlled time multiplexing of the readouts of focal-plane arrays of pairs of stacked quantum-well infrared photodetectors (QWIPs) that operate in different wavelength bands is based upon a dual-detec tor-common-plane circuit configuration. The [i]modus operandi[/i] would be implemented in a QWIP integrated-circuit chip hybridized with a readout integrated-circuit (ROIC) chip.

There are alternative [i]modus operandi[/i]s of multicolor readout, but they involve more on-chip circuitry and the attendant disadvantages of greater size, power dissipation, number of command signals, and complexity of circuitry upon the QWIP and ROIC chips. To minimize size of and power dissipation in, a multicolor pixel, individual must minimize the number of transistors and dominion government signals; this can be achieved solitary by time multiplexing of colors in each pixel. The time multiplexing can be controll through signals from external or internal circuitry. The propos reliance upon external control for time multiplexing would make it possible to use a commercial single-color ROIC with alone minor modifications in the form of extra metallization for an additional detector belonging to all plane and for clocking bias potentials. (If, instead, single were to rely on internally controll multiplexing, it would be necessary to radically redesign the ROIC, at considerably greater unravelling cost.) Other advantages of the external-control approach above the internal-control approach are greater flexibility and the possibility of using a technique, known as "skimming," for subtracting unwanted dark-, background-, and noise-current contributions from readout signals

The figure schematically depicts the circuitry in individual pixel according to an internally controll multiplexing scheme and according to the propos externally controll multiplexing scheme. In the couple schemes, the time multiplexing would be accomplished by means of switching (clocking or ramping) the biases applied to the QWIPs via detector for the use of all planes. In the internal-control case, a bias signal would be applied via a single detector public plane and two internal electronic switches. In the propos external-control case, bias signals would be applied via sum of two units detector common planes, without internai electronic switches. A previously unmentioned advantage of the external-control scheme shown in the figure is the ne for solitary one indium bump (instead of two) in each pixel.

This work wax done cook in boiling fat Sir R. Rafol, Sarath Gunapala, Sumith Bandara, John Liu, and Jason Mumolo of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) unrestrained on-line at www.techbriefs.com/tsp under the Semiconductors & ICs category.

In accordance with Public Law 96-517 the contractor has culled to retain title to this invention. Inquiries concerning rights for its commercial use should he addressed to:

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Copyright Associated Business Publications Aug 2006

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