Activation of p-type layers of tunnel junctions
A method to fabricate micro-size III-nitride light emitting diodes (μLEDs) with an epitaxial tunnel junction comprised of a p+GaN layer, an In x Al y Ga z N insertion layer, and an n+GaN layer, grown using metalorganic chemical vapor deposition (MOCVD), wherein the μLEDs have a low forward voltage. The In x Al y Ga z N insertion layer has a smaller energy bandgap than the GaN layers, which reduces a depletion width of the tunnel junction and increases the tunneling probability. The μLEDs are fabricated with dimensions that vary from 25 to 10,000 μm 2 . It was found that the In x Al y Ga z N insertion layer can reduce the forward voltage at 20 A/cm 2 by at least 0.6 V. The tunnel junction μLEDs with an n-type and p-type In x Al y Ga z N insertion layer had a low forward voltage at 20 A/cm 2 that was very stable. At dimensions smaller than 1600 μm 2 , the low forward voltage is less than 3.2 V.
1 . A method, comprising:
fabricating a III-nitride light emitting diode (LED) structure, wherein:
the III-nitride LED structure includes at least one tunnel junction (TJ) comprised of a p-type III-nitride layer; an n-type III-nitride tunnel junction layer; and an In x Al y Ga z N insertion layer between the p-type III-nitride layer and the n-type III-nitride tunnel junction layer, where 0<x≤1, 0≤y<1, 0≤z≤1, and x+y+z=1; and
the p-type III-nitride layer is activated by removing hydrogen through access points in the n-type III-nitride tunnel junction layer and the In x Al y Ga z N insertion layer that exposes a top surface of the p-type III-nitride layer.
2 . The method of claim 1 , wherein the p-type III-nitride layer and n-type III-nitride tunnel junction layer are comprised of GaN, and the In x Al y Ga z N insertion layer has a lower energy bandgap than the GaN.
3 . The method of claim 1 , wherein the In x Al y Ga z N insertion layer and the n-type III-nitride tunnel junction layer are grown by metalorganic chemical vapor deposition (MOCVD).
4 . The method of claim 1 , wherein the In x Al y Ga z N insertion layer is n-type doped with a donor concentration >1×10 19 cm −3 .
5 . The method of claim 4 , wherein the donor is silicon (Si) or germanium (Ge).
6 . The method of claim 1 , wherein the In x Al y Ga z N insertion layer is p-type doped with a donor concentration >1×10 19 cm −3 .
7 . The method of claim 6 , wherein the donor is magnesium (Mg) or Zinc (Zn).
8 . The method of claim 1 , wherein the p-type III-nitride layer is activated by removing hydrogen through sidewalls of a mesa.
9 . The method of claim 1 , wherein the p-type III-nitride layer is activated by thermal annealing.
10 . The method of claim 1 , wherein selective area growth (SAG) or epitaxial lateral overgrowth (ELOG) is used to make the access points in the n-type III-nitride tunnel junction layer and the In x Al y Ga z N insertion layer.
11 . The method of claim 8 , wherein inductively coupled plasma (ICP) or reactive ion etching (RIE) etching is used to expose the sidewalls of the mesa to access the p-type III-nitride layer.
12 . The method of claim 1 , wherein the III-nitride LED structure comprises a micro-LED with an area less than 10,000 μm 2 .
13 . The method of claim 12 , wherein the III-nitride LED structure has a forward voltage less than 3.45 V at a current density of 20 A/cm 2 .
14 . The method of claim 1 , wherein the n-type III-nitride tunnel junction layer is an n-type GaN layer that contains some indium.
15 . The method of claim 1 , wherein the p-type III-nitride layer is a p-type GaN layer that contains some indium.
16 . A device, comprising:
a III-nitride light emitting diode (LED) structure, wherein:
the III-nitride LED structure includes at least one tunnel junction (TJ) comprised of a p-type III-nitride layer, an n-type III-nitride tunnel junction layer, and an In x Al y Ga z N insertion layer between the p-type III-nitride layer and the n-type III-nitride tunnel junction layer; and
the n-type III-nitride tunnel junction layer and the In x Al y Ga z N insertion layer have one or more access points therein to expose a top surface of the p-type III-nitride layer for removing hydrogen to activate the p-type III-nitride layer.
17 . A device, comprising:
a micro-size III-nitride light emitting diode (LED) comprised of a p-type III-nitride layer, an n-type III-nitride tunnel junction layer, and an In x Al y Ga z N insertion layer between the p-type III-nitride layer and the n-type III-nitride tunnel junction layer, where 0<x≤1, 0≤y<1, 0≤z≤1, and x+y+z=1; and
the p-type III-nitride layer is activated by removing hydrogen through one or more access points in the n-type III-nitride tunnel junction layer and the In x Al y Ga z N insertion layer that expose a top surface of a p-type III-nitride layer.
18 . A device, comprising:
a micro-size III-nitride light emitting diode (LED) with an epitaxial tunnel junction comprised of p+GaN and n+GaN layers with an In x Al y Ga z N insertion layer between the p+GaN and n+GaN layers, where 0<x≤1, 0≤y<1, 0≤z≤1, and x+y+z=1;
the p+GaN layer is activated by removing hydrogen through access points in the n+GaN layer and the In x Al y Ga z N insertion layer that expose a top surface of the p+GaN layer; and
the micro-size III-nitride light emitting diode (LED) having a low forward voltage less than 3.45 V at a current density of 20 A/cm 2 .
19 . The device of claim 18 , wherein the micro-size III-nitride LED has dimensions ranging from 25 to 10,000 μm 2 .
20 . The device of claim 18 , wherein the micro-size III-nitride LED has a size-independent forward voltage at 20 A cm −2 that is stable and uniform around 3.08 V to 3.3V.