Avalanche photodiode with epitaxially regrown guard rings

• US 5,610,416 A
• Filed: 02/16/1995
• Issued: 03/11/1997
• Est. Priority Date: 02/16/1995
• Status: Expired due to Fees

• Current Assignee: Agilent Technologies, Inc.
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Hasnain, Ghulam, Su, Chung-Yi, Hollenhorst, James N.
• Primary Examiner(s): NGO, NGAN V
• Application Number:
  US08/389,375
• Time in Patent Office: 754 Days
• Field of Search: 257/438, 257/186, 257/466, 257/603
• US Class Current: 257/186
• 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 SAM avalanche photodiode formed with an epitaxially regrown guard ring and a planar P-N junction defined between a cap layer and a multiplication layer. The multiplication layer is part of a multi-layer semiconductor platform having a conductivity opposite to the conductivity type of the cap layer, including a light absorption layer, a substrate and an intermediate layer. A second embodiment of the present invention is disclosed including a SAM avalanche photodiode having a guard ring with a variable distribution of impurity dopant concentrations. In addition, a third embodiment of the present invention is disclosed in which a narrow band gap layer completely covers the cap layer and a non-alloy metal contact is formed to completely cover the narrow band gap layer, forming a mirror junction. In this embodiment, incident light is shined through the substrate and reflected from the mirror junction, enhancing the absorption efficiency.

Claims

1. A semiconductor light detector comprising:

a semiconductor platform of a first conductivity type, the semiconductor platform having a multi-layer structure including a light absorption layer and an avalanche multiplication layer, the avalanche multiplication layer having a first impurity dopant concentration;

a cap layer formed of a semiconductor material of a second conductvity type, the cap layer heing positioned proximate to the avalanche multiplication layer, and defining a first P-N junction;

a mesa structure including the cap layer, the first P-N junction, and an upper portion of the avalanche multiplication layer; and

a guard ring of epitaxal semiconductor material of the second conductivity type, the guard ring of epitaxial semiconductor material being positioned proximate to the avalanche multiplication layer and the mesa structure, and surrounding the first P-N junction, the guard ring of epitaxial semiconductor material having a second impurity dopant concentration, the second impurity dopant concentration being less than the first impurity dopant concentration.

2. The semiconductor light detector as recited in claim 1, wherein the first P-N junction is an epitaxial planar junction.

3. The semiconductor light detector as recited in claim 1 wherein the guard ring defines a second P-N junction having a first planar portion, a second planar portion, and a curved portion positioned between the first planar portion and the second planar portion, the second P-N junction being distally positioned from the first P-N junction.

4. The semiconductor light detector as recited in claim 1 wherein both the cap layer and the guard ring are formed of a first semiconductor material, with the guard ring having an impurity dopant concentration less than the impurity dopant concentration of the cap layer.

5. The semiconductor light detector as recited in claim 1 further including a layer of a second semiconductor material of the first conductivity type positioned adjacent to the cap layer, on the side opposite the multiplication layer.

6. The semiconductor light detector as recited in claim 5 further including an ohmic contact positioned adjacent to the layer of the second semiconductor material, forming a mirror junction therebetween, whereby light incident on the mirror junction is reflected therefrom and travels into the absorption layer.

15. The semiconductor light detector as recited in claim 1, further including a layer of a second semiconductor material of the first conductivity type positioned adjacent to the cap layer, on the side opposite the avalanche multiplication layer.

16. The semiconductor light detector as recited in claim 15, further including an ohmic contact positioned adjacent to the layer of the second semiconductor material, forming a mirror junction therebetween, whereby light incident on the mirror junction is reflected therefrom and travels into the absorption layer.

7. A semiconductor light detector, comprising:

a semiconductor platform of a first conductivity type, the semiconductor platform having a multi-layer structure including a light absorption layer and an avalanche multiplication layer;

a cap layer formed of a semiconductor material of a second conductivity type, the cap layer being positioned proximate to the avalanche multiplication layer, defining a first P-N junction;

a mesa structure including the cap layer, the first P-N junction, and an upper portion of the avalanche multiplication layer; and

a guard ring of epitaxial semiconductor material of the second conductivity type, the guard ring of epitaxial semiconductor material being positioned proximate to the avalanche multiplication layer and the mesa structure, and surrounding the first P-N junction, the guard ring of epitaxial semiconductor material having a variable concentration of impurity dopants, a first region of the guard ring being positioned adjacent to the multiplication layer and having a first impurity dopant concentration, and each of the remaining regions of the guard ring having an impurity dopant concentration, the first impurity dopant concentration being less than the concentration of impurity dopants in the multiplication layer.

8. The semiconductor light detector as recited in claim 7 wherein the guard ring and the cap layer are formed of a first semiconductor material of a first conductivity type, with the first impurity dopant concentration being less than the impurity dopant concentration of the remaining regions of the guard ring, the dopant concentration of the remaining regions being at least as concentrated as a dopant concentration of the cap layer.

9. The semiconductor light detector as recited in claim 7 wherein the guard ring and the cap layer are formed of a first semiconductor material of a first conductivity type, with the impurity dopant concentration of the remaining regions being less than the impurity dopant concentration of the first region, the impurity dopant concentration of the first region being less than an impurity dopant concentration of the cap layer.

10. The semiconductor light detector as recited in claim 7 further including a layer of a second semiconductor material of the first conductivity type positioned adjacent to the cap, on the side opposite the multiplication layer.

11. The semiconductor light detector as recited in claim 10 further including a non-alloy ohmic contact positioned adjacent to the layer of second semiconductor material, forming a mirror junction therebetween, whereby light incident on the mirror junction is reflected therefrom to travel into the absorption layer.

12. A semiconductor light detector, comprising:

a semiconductor platform of a first conductivity type, the semiconductor platform having a multi-layer structure including a light absorption layer and an avalanche multiplication layer, the avalanche multiplication layer having a first impurity dopant concentration;

a cap layer formed of an epitaxial semiconductor material, the epitaxial semiconductor material being of a second conductivity type, the cap layer being positioned proximate to the avalanche multiplication layer, and forming a first P-N junction therewith, the first P-N junction being an epitaxial junction;

a mesa structure including the cap layer, the first P-N junction, and an upper portion of the avalanche multiplication layer; and

a guard ring of epitaxial semiconductor material of the second conductivity type, the guard ring of epitaxial semiconductor material being positioned proximate to the avalanche multiplication layer and the mesa structure, and surrounding the first P-N junction, the guard ring having a second impurity dopant concentration, the second impurity dopant concentration being less than the first impurity dopant concentration.

13. The semiconductor light detector as recited in claim 12, wherein the guard ring defines a second P-N junction having a first planar portion, a second planar portion, and a curved portion positioned between the first planar portion and the second planar portion, the second P-N junction being distally positioned from the first P-N junction.

14. The semiconductor light detector as recited in claim 12, wherein both the cap layer and the guard ring are formed of a first semiconductor material, with the guard ring having an impurity dopant concentration less than the impurity dopant concentration of the cap layer.