SEMICONDUCTOR PHOTODETECTOR WITH TRANSPARENT INTERFACE CHARGE CONTROL LAYER AND METHOD THEREOF

• US 20110291108A1
• Filed: 05/24/2011
• Published: 12/01/2011
• Est. Priority Date: 05/25/2010
• Status: Active Grant

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: United States Secretary of the Army
• Inventors: Wraback, Michael, Sampath, Anand V., Shen, Paul H.
• Granted Patent: US 8,269,222 B2
• Time in Patent Office: Days
• US Class Current: 257/77
• CPC Class Codes: H01L 31/03687 including microcrystalline AIVBIV alloys, e.g. uc-SiGe, uc-SiC
• CPC Class Codes: H01L 31/105 the potential barrier being of the PIN type
• CPC Class Codes: H01L 31/107 the potential barrier working in avalanche mode, e.g. avalanche photodiodes
• CPC Class Codes: H01L 31/1812 including only AIVBIV alloys, e.g. SiGe
• CPC Class Codes: Y02E 10/548 Amorphous silicon PV cells

Abstract

A detection device comprising a photodetector comprising a first semiconductor layer through which light first enters the photodetector; the first semiconductor layer to semiconductor material crystal lattice which terminates at an interface; the discontinuity of the semiconductor crystal lattice at the interface creating a first interface charge; the first semiconductor layer being an absorption layer in which photons in a predetermined wavelength range are absorbed and create photogenerated carriers; and a second polar semiconductor layer deposited on the crystal lattice of the first semiconductor layer, the second polar semiconductor being substantially transparent to light in the predetermined wavelength range, the second polar semiconductor layer having a total polarization different from the first semiconductor layer so that a second interface charge is induced at the interface between the first and second semiconductor layers; the induced second interface charge reduces or substantially cancels the first interface charge; whereby the reduction or substantial cancellation of the surface charge in the first semiconductor layer increases the collection of photogenerated carriers by the photodetector. A method of improving the quantum efficiency of a semiconductor photodetector comprising providing a semiconductor photodetector having a first layer which has a first interface through which light first enters the semiconductor photodetector; placing a layer of polar material transparent to the band of detection wavelengths that has a polarization substantially different than the polarization of the first layer such that the polarization charge induced at the interface between the layer of polar material and the first surface results in decreased interface recombination of photogenerated minority carriers and an increase in quantum efficiency of the photodetector.

Claims

1. A detection device comprising:

a photodetector comprising a first semiconductor layer through which light first enters the photodetector;

the first semiconductor layer formed of a first semiconductor material crystal lattice which terminates at an interface;

the discontinuity of the semiconductor crystal lattice at the interface creating a first interface charge;

the first semiconductor layer being an absorption layer in which photons in a predetermined wavelength range are absorbed and create photogenerated carriers; and

a second polar semiconductor layer deposited on the crystal lattice of the first semiconductor layer, the second polar semiconductor being substantially transparent to light in the predetermined wavelength range, the second polar semiconductor layer having a total polarization different from the first semiconductor layer so that a second interface charge is induced at the interface between the first and second semiconductor layers;

the induced second interface charge reduces or substantially cancels the first interface charge;

whereby the reduction or substantial cancellation of the surface charge in the first semiconductor layer increases the collection of photogenerated carriers by the photodetector.

2. The detection device of claim 1 wherein the first layer is made of a polar material.

3. The detection device of claim 1 wherein the first semiconductor layer is n-type and the second polar semiconductor layer has a total polarization that is substantially greater than the polarization of the first polar semiconductor layer such that the positive induced polarization charge cancels the negative interface charge.

4. The detection device of claim 1 wherein the first semiconductor layer is p-type and the second polar semiconductor layer has a total polarization that is substantially less than the polarization of the first polar semiconductor layer such that the negative induced polarization charge cancels the positive interface charge.

5. The detection device of claim 1 further comprising first and second electrical contacts or electrical contact layers.

6. The detection device of claim 1 wherein the second semiconductor layer is doped and an electrical contact is made to the second semiconductor layer.

7. The detection device of claim 1 wherein the second polar semiconductor layer has a wider band gap than the first semiconductor layer.

8. The detection device of claim 1 wherein the detection device operates to detect light within a predetermined wavelength range and the second polar semiconductor layer is formed of polar material that is substantially transparent to light within the predetermined wavelength range such that photo-generated carriers are not substantially created within the second polar semiconductor layer.

9. The detection device of claim 1 wherein the thickness of the second polar semiconductor layer is such that the photon flux entering the first semiconductor layer is maximized such that no additional antireflection layer is necessary.

10. The detection device of claim 1 wherein the first semiconductor layer is n-type and the interface terminates with negative first interface charge due to breakdown of periodicity of the crystal lattice creating states which are occupied by electrons thereby creating a negative first interface charge which diminishes collection of minority carriers photogenerated near the interface, and by placing a second polar semiconductor layer with a larger polarization at the interface of the first polar semiconductor, the first interface charge is cancelled or diminished thereby substantially eliminating the effect of the first interface charge on the collection of minority carriers photogenerated near the interface.

11. The detection device of claim 1 wherein the addition of the second polar semiconductor layer enables the collection of carriers photogenerated near the interface by higher energy photons to enhance short wavelength performance.

12. The detection device of claim 1 wherein the second polar semiconductor layer is formed of a material comprising one of a material selected from a group consisting of a group III-V Nitride, group III-V Arsenide, group III-V Antimonide, or group II-VI Oxide material.

13. The detection device of claim 1 wherein the second polar semiconductor layer is grown on the first semiconductor layer by an epitaxial process such as MBE or MOCVD.

14. The detection device of claim 1 wherein the second polar semiconductor layer is one of boron nitride, boron aluminum nitride, boron aluminum gallium nitride, aluminum indium gallium nitride, aluminum indium nitride, aluminum nitride that is substantially transparent at wavelengths shorter than approximately 266 nm.

15. The detection device of claim 14 wherein the light detector is a a p-down SiC avalanche photodetector wherein the first semiconductor layer is n-type.

16. A light detector comprising:

a primary semiconductor layer comprising an optically exposed photon reception region;

a secondary semiconductor layer adjacent to and having total polarization different, from the primary semiconductor layer so that an interface charge is induced at the interface between the primary and secondary semiconductor layers;

the induced charge reduces or substantially cancels the interface charge caused by the discontinuity of the semiconductor lattice of the primary semiconductor at the interface; and

a photodetection element which converts the photon flux to electric current;

whereby the reduction or cancellation of the interface charge in the primary semiconductor layer increases the collection of photogenerated earners generated by photons having energy larger than the bandgap of the first semiconductor layer by the photodetection element.

17. The detector of claim 16 wherein the secondary semiconductor layer is formed of a material comprising one of a material selected from a group consisting of a group III-V Nitride, group III-V Arsenide, group III-V Antimonide, or group II-VI oxide material.

18. The detector of claim 16, wherein the secondary semiconductor layer has a total polarization that is sufficiently different than the polarization of the primary semiconductor layer such that the induced polarization charge cancels the surface charge associated with the density of surface states in the primary semiconductor layer.

19. A method of improving the quantum efficiency of a semiconductor photodetector comprising:

providing a semiconductor photodetector having a first layer which has a first interface through which light first enters the semiconductor photodetector;

placing a layer of polar material transparent to the band of detection wavelengths that has a polarization substantially different than the polarization of the first layer such that the polarization charge induced at the interface between the layer Of polar material and the first surface results in decreased interface recombination of photogenerated minority carriers and an increase in quantum efficiency of the photodetector.

20. The method of claim 19 wherein the semiconductor photodetector is a p-down SiC avalanche photodetector wherein the first layer is n-type and wherein the step of placing a layer of polar material comprises placing a layer of a group III-Nitride material thereon.