Avalanche photo diode and method of manufacturing the same
The inventive concept provides avalanche photo diodes and methods of manufacturing the same. The avalanche photo diode may include a substrate, a light absorption layer formed on the substrate, a clad layer formed on the light absorption layer, an active region formed in the clad layer, a guard ring region formed around the active region, and an insulating region formed between the guard ring region and the active region.
1. An avalanche photo diode comprising:
a substrate;
a light absorption layer formed on the substrate;
a clad layer formed on the light absorption layer;
an active region formed in the clad layer;
a guard ring region formed around the active region; and
an insulating region formed between the guard ring region and the active region and including a trench having a predetermined depth, the insulating region reducing or minimizing a dark current induced along a top surface of a clad layer between the active region and the guard ring region, and
a passivation layer covering the insulating layer and the guard ring region.
2. The avalanche photo diode of claim 1 , wherein the insulating region includes a gapfill layer filling the trench formed in the clad layer between the guard ring region and the active region.
3. The avalanche photo diode of claim 2 , wherein the gapfill layer has a depth substantially equal to a depth of the guard ring region in the clad layer.
4. The avalanche photo diode of claim 2 , wherein the gapfill layer includes a silicon nitride layer.
5. The avalanche photo diode of claim 4 , wherein the passivation layer includes the same silicon nitride layer as the gapfill layer.
6. The avalanche photo diode of claim 1 , wherein the active region and the guard ring region are doped impurities of the same conductivity type.
7. The avalanche photo diode of claim 1 , further comprising:
a top electrode formed on the active region; and
a bottom electrode disposed on a back side of the substrate and having a portion exposing a light receiving region in the back side of the substrate opposite to the top electrode.
8. The avalanche photo diode of claim 1 , further comprising:
a grading layer formed between the light absorption layer and the clad layer; and
a buffer layer formed between the grading layer and the clad layer.
9. The avalanche photo diode of claim 8 , wherein the substrate, the buffer layer, and the clad layer include indium-phosphorus; and
wherein the grading layer and the light absorption layer include indium-gallium-arsenic-phosphorus.
10. The avalanche photo diode of claim 1 , wherein the substrate, the light absorption layer, and the clad layer are doped with impurities of a first conductivity type; and
wherein the active region and the guard ring region are doped with impurities of a second conductivity type.
11. The avalanche photo diode of claim 1 , wherein a center portion of the active region has a thickness greater than that of an edge portion of the active region adjacent to the insulating region.
12. The avalanche photo diode of claim 1 , wherein an upper surface of the clad layer includes a first portion disposed between the active region and the trench and a second portion disposed between the trench and the guard ring region, and the first portion is disposed at a level the same as a level at which the second portion is disposed.
13. The avalanche photo diode of claim 1 , wherein the insulating region is spaced apart from the guard ring region and the active region, and an upper surface of the insulating region is at the same level with an upper surface of the clad layer.