Photodiode and photodiode array with improved performance characteristics

• US 8,816,464 B2
• Filed: 12/21/2012
• Issued: 08/26/2014
• Est. Priority Date: 08/27/2008
• Status: Expired due to Fees

• Current Assignee: OSI Optoelectronics, Inc. (OSI Systems Incorporated)
• Original Assignee: OSI Optoelectronics, Inc. (OSI Systems Incorporated)
• Inventors: Bui, Peter Steven, Taneja, Narayan Dass
• Primary Examiner(s): PRENTY, MARK V
• Application Number:
  US13/725,803
• Publication Number:
  US 20130277786A1
• Time in Patent Office: 613 Days
• Field of Search: 257/461, 257/432, 257/436, 257/437, 257/443, 438/57, 250/370.11
• US Class Current: 257/461
• CPC Class Codes: G01T 1/20183 Arrangements for preventing or correcting crosstalk, e.g. optical or electrical arrangements for correcting crosstalk
• CPC Class Codes: H01L 31/02161 for devices characterised by at least one potential jump barrier or surface barrier
• CPC Class Codes: H01L 31/0232 Optical elements or arrangements associated with the device H01L31/0236 takes precedence; for photovoltaic cells H01L31/054; for photovoltaic modules H02S40/20
• CPC Class Codes: H01L 31/02322 comprising luminescent members, e.g. fluorescent sheets upon the device
• CPC Class Codes: H01L 31/118 of the surface barrier or shallow PN junction detector type, e.g. surface barrier alpha-particle detectors
• CPC Class Codes: H01L 31/18 Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof

Abstract

The present invention is a photodiode and/or photodiode array, having a p+ diffused area that is smaller than the area of a mounted scintillator crystal, designed and manufactured with improved device characteristics, and more particularly, has relatively low dark current, low capacitance and improved signal-to-noise ratio characteristics. More specifically, the present invention is a photodiode and/or photodiode array that includes a metal shield for reflecting light back into a scintillator crystal, thus allowing for a relatively small p+ diffused area.

Claims

1. A photodiode comprising:

a substrate having at least a front side and a back side;

a scintillator, wherein said scintillator is located on the front side of the photodiode;

a p+ diffused region located on said front side, wherein said p+ diffused region has a length of 1 mm or less and has a width of 1 mm or less;

at least one back side contact; and

at least one front side contact.

2. The photodiode of claim 1 wherein said substrate has a resistivity less than 2000 ohm cm.

3. The photodiode of claim 1 further comprising a reflective metal shield on at least a portion of said front side, wherein said metal shield reflects incident light back into said scintillator.

4. The photodiode of claim 1 wherein said scintillator is a crystal and wherein said crystal is mounted on the front side of the photodiode.

5. The photodiode of claim 3 wherein the reflective metal shield comprises aluminum.

6. The photodiode of claim 1, wherein a distance between the p+diffused region and an edge of the photodiode ranges from 0.3 mm to 0.5 mm.

7. The photodiode of claim 1 further comprising an anti-reflective layer formed from SiO₂.

8. The photodiode of claim 1 further comprising an anti-reflective layer formed from SiO₂ having a thickness of 150 Å

and Si₃N₄ having a thickness of 400Å

, for a total layer thickness of 550 Å

.

9. A photodiode array, comprising:

a substrate having a front side and a back side;

a plurality of diode elements integrally formed in the substrate, wherein each diode element has a p+ diffused region on said front side and wherein said p+ diffused region has a length of 1 mm or less and has a width of 1 mm or less;

a plurality of scintillators, wherein each diode element has at least one scintillator located on the front side thereof; and

at least one front side contact.

10. The photodiode array of claim 9 further comprising a reflective metal shield on at least a portion of said front side of each diode element, wherein said metal shield reflects incident light back into the scintillator.

11. The photodiode array of claim 9 wherein said scintillator comprises crystal and wherein said crystal is mounted on the front side of the diode element.

12. The photodiode array of claim 9 wherein said substrate has a resistivity greater than 1000 ohm cm.

13. The photodiode array of claim 9 further comprising a back side contact, wherein said back side contact is a cathode.

14. The photodiode array of claim 9 wherein said front side contact is an anode.

15. The photodiode array of claim 9 wherein said scintillator comprises a crystal, wherein said crystal has a first dimension of 2 mm and a second dimension of 2 mm.

16. The photodiode array of claim 9 wherein the substrate has a resistivity in a range of 1000 ohm cm to 2000 ohm cm.