Device having strain induced region of altered bandgap

• US 4,772,924 A
• Filed: 11/25/1987
• Issued: 09/20/1988
• Est. Priority Date: 11/18/1985
• Status: Expired due to Term

• Current Assignee: Agere Systems Incorporated (Broadcom, Inc.)
• Original Assignee: David V. Lang, Henryk Temkin, John C. Bean, Roosevelt People, Thomas P. Pearsall
• Inventors: Pearsall, Thomas P., Lang, David V., Temkin, Henryk, People, Roosevelt, Bean, John C.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/129,942
• Time in Patent Office: 300 Days
• Field of Search: 357/4 SL, 357/4, 357/30 A, 357/30 N, 357/13, 357/16
• US Class Current: 257/19
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01L 31/035254 including, apart from doping materials or other impurities, only elements of Group IV of the Periodic Table, e.g. Si-SiGe superlattices
• CPC Class Codes: H01L 31/1075 in which the active layers, e.g. absorption or multiplication layers, form an heterostructure, e.g. SAM structure

Abstract

A strained layer superlattice comprising Ge_x Si_1-x layers interleaved with Si layers is an excellent photodetector at infrared wavelengths due to the large shift in bandgap caused by the strain in the superlattice.

Claims

1. A device comprising a substrate and disposed thereon a first cladding layer, an interleaved region of alternating first and second compositions comprising Ge_x Si_1-x and Ge_y Si_1-y, respectively, x greater than y and less than or equal to 1.0, having different lattice constants and a lattice mismatch, said mismatch being accommodated by strain thereby changing the bandgap from that of the bulk compositions and at least one of said x and y being selected to yield the strain induced bandgap.

2. A device as recited in claim 1 further comprising a second cladding layer on the side of said interleaved region opposite to that of said first cladding layer.

3. A device as recited in claim 2 in which said first and second clading layers have opposite conductivity types.

4. A device as recited in claim 3 in which x and y are essentially constant in said strained layer region.

5. A device as recited in claim 4 in which said first and second cladding layers comprise silicon.

6. A device as recited in claim 5 further comprising a third layer of silicon having intrinsic conductivity and being between said second layer and said interleaved region.

7. A device as recited in claim 6 further comprising a fourth layer of silicon having a first conductivity type and being between said third layer and said interleaved region.

8. A device as recited in claim 7 in which said first conductivity type is n-type.

9. A device as recited in claim 5 in which x is between approximately 0.4 and approximately 0.6.

10. A device as recited in claim 1 in which said substrate comprising Si having an orientation selected from the group consisting of (100) and (110).

11. A device comprising a substrate and disposed thereon a first layer comprising Ge_x Si_1-x, x greater than 0.0 and less thanor equal to 1.0, having a different lattice constant than said substrate and a lattice mismatch, said mismatch being accommodated by strain thereby changing the bandgap from that of the bulk composition and said x being selected to yield the strain induced bandgap.

12. A device as recited in claim 11 in which said substrate comprises Si.

13. A device as recited in claim 12 further comprising a second layer comprising Ge_y Si_1-y, y greater than or equal to 0.0 and less than 1.0, x not equal to y, sid second layer being disposed on said first layer, said first and second layers comprising a pair of layers.

14. A device as recited in claim 13 in which said first alyer and said second layers have opposite conductivity types.

15. A device as recited in claim 14 further comprising first and second electrical contacts to said substrate and second layer, respectively.

16. A device as recited in claim 15 in which said substrate and said second layer have the same conductivity types.

17. A device as recited in claim 16 in which y is less than x.

18. A device as recited in claim 17 further comprising a third electrical contact to said second layer.

19. A device as recited in claim 13 further comprising first and second electrical contacts to said second layer.

20. A device as recited in claim 13 comprising a plurality of said pairs.