CdHgTe photodiodes array

Patent metadata

Field	Value
Publication number	US-9397244-B2
Application number	US-201514686084-A
Country	US
Kind code	B2
Filing date	Apr 14, 2015
Priority date	Apr 22, 2014
Publication date	Jul 19, 2016
Grant date	Jul 19, 2016

Abstract

A photodiodes array includes a useful layer made of Cd x Hg 1-x Te; first doped zones each forming a PN junction with a second doped zone surrounding the first doped zones. The array includes regions located between two PN junctions, with a cadmium concentration gradient decreasing from the upper face to the lower face of the useful layer. A method of making such a photodiodes array includes producing, on the upper face of the useful layer, of a structured layer with at least one through opening, and with a cadmium concentration higher than the cadmium concentration in the useful layer; annealing the useful layer covered by the structured layer, with diffusion of cadmium atoms of the structured layer, from the structured layer to the useful layer; producing at least two PN junctions in the useful layer.

First claim

The invention claimed is:

1. A photodiodes array comprising:
a useful layer made of a semiconducting alloy of cadmium, mercury and tellurium of the Cd x Hg 1-x Te type, the useful layer having an upper face and a lower face;
at least two first doped zones, located in the useful layer, each forming a PN junction with a second doped zone surrounding the first doped zones, the PN junctions being flush with the upper face of the useful layer;
wherein the array comprises at least one region, located between two neighbouring PN junctions, and has a cadmium concentration gradient decreasing from the upper face to the lower face of the useful layer.

2. The array according to claim 1 , wherein the average concentration of cadmium in said region is higher than the average concentration of cadmium in the remainder of the useful layer.

3. The array according to claim 1 , wherein said region extends between two PN junctions, and outside each first doped zone.

4. The array according to claim 3 , wherein said region extends in the useful layer deeper than the first doped zones.

5. The array according to claim 1 , wherein said region extends between two PN junctions, and in an upper peripheral volume of each of the first doped zones.

6. The array according to claim 5 , wherein said region extends in the useful layer less deep than the first doped zones.

7. The array according to claim 5 , wherein said region extends in a first doped zone over less than half of the volume of this first doped zone.

8. The array according to claim 1 , wherein said region has:
a first portion extending outside the first doped zones; and
a second portion extending in an upper peripheral volume of at least one first doped zone;
the first portion extending deeper in the useful layer than the second portion, and the first portion being surrounded by the second portion.

9. The array according to claim 1 , wherein the first doped zone is P-doped by arsenic atoms.

10. A method of fabrication of a photodiodes array according to claim 1 , comprises the following steps:
producing, on the upper face of the useful layer, a structured layer with at least one through opening, and with a cadmium concentration higher than the cadmium concentration in the useful layer;
annealing of the useful layer covered by the structured layer, with diffusion of cadmium atoms of the structured layer, from the structured layer to the useful layer;
producing at least two PN junctions in the useful layer.

11. The method according to claim 10 , wherein the production of a structured layer involves:
depositing of a reservoir layer on the upper face of the useful layer; and
etching of at least one through opening in the reservoir layer, the etching being a chemical etching.

12. The method according to claim 10 , wherein the steps of production of a structured layer and annealing form a fabrication cycle, and at least two fabrication cycles are implemented.

13. The method according to claim 10 , wherein the step of production of the PN junctions make use of an arsenic ion implantation.

14. The method according to claim 10 , wherein annealing is done at a temperature of between 100° C. and 500° C.

15. The method according to claim 14 , wherein annealing is done for a duration of between 1 hour and 100 hours.

Assignees

• Commissariat Energie Atomique
• Commissariat Energie Atomique

Inventors

• Mollard Laurent
• Bourgeois Guillaume
• Destefanis Gerard

Classifications

• H10F77/1233

  characterised by the dopants · CPC title

• H10F77/148

  Shapes of potential barriers · CPC title

• H10F71/1253

  comprising at least three elements, e.g. HgCdTe · CPC title

• H10F39/107

  having multiple elements covered by H10F30/00 in a repetitive configuration, e.g. radiation detectors comprising photodiode arrays · CPC title

• H10F39/103

  the at least one element covered by H10F30/00 having potential barriers, e.g. integrated devices comprising photodiodes or phototransistors · CPC title