Electromagnetic radiation detectors

• US 4,614,957 A
• Filed: 12/04/1984
• Issued: 09/30/1986
• Est. Priority Date: 03/31/1982
• Status: Expired due to Fees

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Wood, R. Andrew, Arch, David K., Smith, Darryl L., Scott, M. Walter, Weisberg, Leonard R.
• Primary Examiner(s): Edlow, Martin H.
• Application Number:
  US06/677,336
• Time in Patent Office: 665 Days
• Field of Search: 357/30, 357/16, 357/61, 357/56
• US Class Current: 257/188
• CPC Class Codes: H01L 21/44 Manufacture of electrodes on semiconductor bodies using processes or apparatus not provided for in groups H01L21/38 - H01L21/428
• CPC Class Codes: H01L 31/02966 including ternary compounds, e.g. HgCdTe
• CPC Class Codes: H01L 31/03046 including ternary or quaternary compounds, e.g. GaAlAs, InGaAs, InGaAsP
• CPC Class Codes: H01L 31/09 Devices sensitive to infrared, visible or ultraviolet radiation H01L31/101 takes precedence
• CPC Class Codes: H01L 31/109 the potential barrier being of the PN heterojunction type
• CPC Class Codes: Y02E 10/544 Solar cells from Group III-V materials

Abstract

An improved electromagnetic radiation-sensitive semiconductor device together with a method of making same is disclosed in which surface regions directly beneath the active portion of the electrical contacts are provided with a layer of semiconductor material having a higher bandgap than the radiation sensitive material which repels minority carriers but allows the passage of majority carriers. Because the rate of annihilation of minority carriers at the contact to which they are attracted is reduced, the responsivity of the detector is greatly enhanced.

Claims

1. A photoconductive semiconductor device comprising:

a substrate;

a first layer of electromagnetic radiation sensitive semiconductor material of a given conductivity type and having a first energy bandgap on said substrate;

a first region of a second layer of semiconductor material of the same conductivity type as said first layer of semiconductor material, but having a second energy bandgap greater than said first bandgap, and in electrical contact with said first layer; and

a first ohmic contact means on and in electrical communication with said region of said second layer of semiconductor material and adapted to be connected to a first conductor of an external source of electrical voltage in a manner such that said first ohmic contact will attract minority carriers;

a second ohmic contact means on and in electrical communication with either said first or said second layer of semiconductor material and adapted to be connected to a second conductor of said external source of electrical voltage of opposite polarity to said first contact of said external source of electrical voltage; and

wherein said first and second ohmic contact means on said semiconductor material are spaced from each other a sufficient distance such that external electromagnetic radiation may be sensed in the space therebetween.

3. The semiconductor device according to claim 1 wherein both of said ohmic contact means are on and in electrical communication with said second layer of semiconductor material.

5. The semiconductor device according to any of claims 1, 2, 3 or 4 wherein said first layer of semiconductor material comprises Hg_1-x Cd_x Te and where x is a number having a value between 0.1 and 0.4.

6. The semiconductor device according to claim 5 wherein said first layer of semiconductor material is Hg_1-x Cd_x Te and wherein x is a number between 0.1 and 0.4;

and wherein said second layer of semiconductor material comprises Hg_1-y Cd_y Te wherein y is a number greater than x but less than unity.

7. The semiconductor device according to claim 6 wherein y exceeds x by at least 0.01.

8. The semiconductor device according to any of claims 1, 2, 3 or 4 wherein said first layer of semiconductor material is produced on said substrate by epitaxial formation.

9. The semiconductor device according to any of claims 1, 2, 3 or 4 wherein both said layers of semiconductor material are produced by liquid phase epitaxy.

10. The semiconductor device according to either of claims 3 or 4 wherein said second layer of semicondcutor material is coextensive with said first layer.

11. The semiconductor device according to either of claims 3 or 4 further comprising a second region of said second layer of semiconductor material substantially identical to said first region of said second layer of semiconductor material on said first layer of semiconductor material;

and wherein said second ohmic contact is connected on said second region of said second layer of semiconductor material.

12. The semiconductor device according to any of claims 1, 2, 3 or 4 wherein said semiconductor material in both said layers is n-type.

13. A semiconductor device according to either of claims 1 or 2 wherein said first layer of said electromagnetic radiation-sensitive semiconductor material is one selected from the group consisting of InAs_x Sb_1-x, In_x Ga_1-x Sb, and Pb_1-x Sn_x Te wherein x has a value greater than zero but less than unity.

2. A photoconductive semiconductor device comprising:

a substrate;

a first layer of electromagnetic radiation-sensitive semiconductor material of a given conductivity type and comprising a plurality of elemental species of a first percentage composition which produces a first energy bandgap;

a first region of a second layer of electromagnetic radiation sensitive semiconductor material of the same conductivity type and comprising the same plurality of elemental species as said first layer of semiconductor material on said first layer of semiconductor material, but having a second percentage composition which produces a second energy bandgap greater than said first energy bandgap;

a first ohmic contact means on and in electrical communication with said region of said second layer of semiconductor material and adapted to be connected to a first conductor of an external source of electrical voltage in a manner such that said first ohmic contact will attract minority carriers; and

a second ohmic contact means on and in electrical communication with either said first or said second layer of semiconductor material and adapted to be connected to a second conductor of said external source of electrical voltage of opposite polarity to said first contact of said external source of electrical voltage; and

wherein said first and second ohmic contact means on said semiconductor material are spaced from each other a sufficient distance such that external electromagnetic radiation may be sensed in the space therebetween.

4. The semiconductor device according to claim 2 wherein both of said ohmic contact means are on and in electrical communiction with said second layer of semiconductor material.

14. A photoconductive semiconductor device comprising:

a substrate;

a first layer of Hg_1-x Cd_x Te of a given conductivity type on said substrate, wherein x is a number having a value between 0.1 and 0.4;

a first region of a second layer of Hg_1-y Cd_y Te having the same conductivity type as said first layer of Hg_1-x Cd_x Te material, wherein y is a number having a value greater than x but less than unity, on said first layer of semiconductor material; and

a first ohmic contact means on and in electrical communication with said region of said second layer of semiconductor material and adapted to be connected to a first conductor of an external source of electrical voltage in a manner such that said first ohmic contact with attract minority carriers; and

a second ohmic contact means on and in electrical communication with either said first or said second layer of semiconductor material and adapted to be connected to a second conductor of said external source of electrical voltage of opposite polarity of said first contact of said external source of electrical voltage; and

wherein said first and second ohmic contact means on said semiconductor material are spaced from each other a sufficient distance such that external electromagnetic radiation may be sensed in the space therebetween.

15. A semiconductor device according to claim 14 wherein said conductivity is n-type.

16. The semiconductor device according to claim 14 wherein both of said ohmic contact means are on and in electrical contact with said second layer of semiconductor material.

17. The semiconductor device according to claim 14 wherein said second layer of semiconductor material is coextensive with said first layer and wherein both of said ohmic contact means are on and in electrical contact with said second layer of semiconductor material.

18. The semiconductor device according to claim 14 further comprising a second region of said second layer of semiconductor material substantially identical to said first region of semiconductor material on said first layer of semiconductor material;

and wherein said second ohmic contact is on and in electrical communication with to said second region of said second layer of semiconductor material.

19. A semiconductor device according to any of claims 14 through 18 wherein said layer in said regions of Hg_1-x Cd_x Te and Hg_1-y Cd_y Te are formed by epitaxial growth.

20. A semiconductor device according to claim 19 wherein said epitaxial growth is liquid phase epitaxy.

21. The semiconductor device according to claim 19 wherein said epitaxial growth is vapor phase epitaxy.

22. A semiconductor device according to any of claims 14 through 18 wherein said layer of Hg_1-x Cd_x Te has a thickness from about 5×

10^-4 cm to about 15×

10^-4 cm and said layer of Hg_1-y Cd_y Te has a thickness from about 10^-4 cm to 10^-3 cm.