Infrared radiation-detecting device
AssigneeCalifornia Institute of Technology
InventorsSarath Gunapala, John K. Liu, Jin S. Park, True-Lon Lin, Mani Sundaram
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Abstract
An AlxGa1−xAs/GaAs/AlxGa1−xAs quantum well exhibiting a bound-to-quasibound intersubband absorptive transition is described. The bound-to-quasibound transition exists when the first excited state has the same energy as the “top” (i.e., the upper-most energy barrier) of the quantum well. The energy barrier for thermionic emission is thus equal to the energy required for intersubband absorption. Increasing the energy barrier in this way reduces dark current. The amount of photocurrent generated by the quantum well is maintained at a high level.
Claims32
A quantum well infrared photodetector, comprising:
- a plurality of periods, each period having a barrier layer and a well layer, each well layer of each period coupled between two barrier layers,
- each well having a well bottom, and a well top, and each well supporting bound energy states therein,
- each of said plurality of periods being selected such that a bound energy state is substantially resonant with said well top.
A quantum well photodetector, comprising:
- a radiation detecting surface;
- a photodetector element, having
- a plurality of periods, each period having a barrier layer of a first semiconductor material and a well layer of a second semiconductor material, said first and second materials defining a band gap therebetween, each well layer of each period coupled between two barrier layers, each well having a well bottom, and a well top, and each well supporting an unexcited energy state for photocarriers, and a bound excited energy state for photocarriers, said photocarriers excited by radiation into said bound excited energy state,
- each of said plurality of said periods being selected such that a bound energy state is substantially resonant with said well top.
A quantum well semiconductor, comprising:
- a plurality of quantum well structures, each said quantum well structure having a barrier layer of a first semiconductor material and a well layer of a second semiconductor material, said first and second materials defining a band gap therebetween, each well layer of each period coupled between two barrier layers, each well having a well bottom, and a well top, and each well supporting an unexcited energy state, and a bound excited energy state for photocarriers,
- each of said plurality of said wells being selected such that the bound excited energy state is substantially resonant with a top portion of the well.
A bound-to-quasibound quantum well semiconductor comprising:
- a well layer comprising a first semiconducting material, said well layer having a first abutting surface and a second abutting surface;
- and
- first and second barrier layers, each comprising a second semiconducting material different than the first semiconducting material, said first barrier layer having a first surface that is attached to said first abutting surface of said well layer, and said second barrier layer having a first surface that is attached to said second abutting surface of said well layer,
- each of said plurality of layers selected to have an excited-state energy level which is substantially the same energy as an energy level that defines a top of the quantum well.
A method for reducing the thickness of a substrate attached to a quantum well, comprising:
- growing a stop-etch layer on a top surface of the substrate;
- growing the quantum well on the stop-etch layer;
- removing a first layer from a bottom surface of the substrate with an abrasive polishing solution;
- removing a second layer from the bottom surface of the substrate with a chemical polishing solution;
- removing a third layer from the bottom surface of the substrate with a wet chemical etching solution;
- and,
- removing more of the substrate with a plasma etching process.
Dependencies are inferred from the claim text.