Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Patent
1988-10-05
1990-05-15
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
25037013, 357 30, H01J 4014
Patent
active
049260383
ABSTRACT:
A HgCdTe heterojunction photodiode and array of same has a multilayered, modulated multi-quantum well (MMQW) structure 12 interposed between a radiation absorbing base region 10 and an overlying current collector region 18. The MMQW structure is comprised of a plurality of alternating thin layers of wide bandgap CdTe 14 and narrow bandgap HgTe 16 material which together form a plurality of quantum wells in the conduction band. The width of each of the wells is defined by the physical thickness of a corresponding one of the HgTe layers, the width being modulated or varied across the MMQW structure. This variation in HgTe layer width varies the energy of the quantized electronic ground state of each well, wider width wells being associated with higher-lying, less tightly bound, ground states. The thickness of the HgTe layers, and hence the width of each of the wells, is selected such that the ground energy levels of each of the wells will "line-up" within a range of reverse bias potential. A transmission resonance is thus provided for minority charge carriers at their band edge in the base region while simultaneously blocking the transmission of other charge carriers. This results in the unimpeded flow of photocurrent across the device heterojunction while suppressing the tunnelling and g-r components of the dark current.
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Allen Stephone B.
Denson-Low W. K.
Nelms David C.
Santa Barbara Research Center
Schubert W. C.
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