Metal organic chemical vapor depostion (MOCVD) tunnel junction growth in III-nitride devices
A method for fabricating an (Al,Ga,In,B)N or III-nitride semiconductor device, including performing a growth of III-nitride or (Al,Ga,In,B)N material including a p-n junction with an active region and using metal-organic chemical vapor deposition (MOCVD) or chemical vapor deposition; and performing a subsequent regrowth of n-type (Al,Ga,In,B)N or III-nitride material using MOCVD or chemical vapor deposition while utilizing a pulsed delta n-type doping scheme to realize an abrupt, smoother surface of the n-type material and a higher carrier concentration in the n-type material. In another example, the method comprises forming a mesa having a top surface; and activating magnesium in the p-type GaN of the (Al,Ga,In,B)N material through openings in the top surface that expose the p-type GaN's surface. The openings are formed before or after the subsequent regrowth of the tunnel junction.
1 . A device, comprising:
a mesa including:
a III-nitride p-n junction, the p-n junction including an active region between a first p-type layer and a first n-type layer; and
a III-nitride region patterned on the III-nitride p-n junction, the III-nitride region including a second n-type layer, a second p-type layer, and a tunnel junction formed at an interface between the second n-type layer and the second p-type layer;
an array of openings in the III-nitride region on a top of the mesa and through the second n-type layer so as to expose the second p-type layer underlying the second n-type layer; and
a first metal contact to the first n-type layer and a second metal contact to the second n-type layer, wherein the device comprises a light emitting device outputting light in response to a current density flowing between the first metal contact and the second metal contact.
2 . The device of claim 1 , wherein each of the openings have a width W and 0.1 μm≤W≤100 μm.
3 . The device of claim 2 , wherein a spacing S between the openings is 0.5 μm≤S≤400 μm.
4 . The device of claim 1 , further comprising a patterned dielectric on a top surface of the mesa, wherein the patterned dielectric comprises the array of the openings exposing the second p-type layer.
5 . The device of claim 1 , wherein the first p-type layer, the second p-type layer, the first n-type layer, and the second n-type layer comprise GaN.
6 . The device of claim 1 , wherein the second n-type layer comprises an n-type GaN layer having an n-type dopant concentration of at least 1.1E20 cm −3 .
7 . The device of claim 1 , wherein the interface has a surface roughness of 2.2 nm or less over an area of 5 micrometers by 5 micrometers.
8 . A method for fabricating a semiconductor device, comprising:
growing a III-nitride p-n junction with an active region using metal-organic chemical vapor deposition (MOCVD) and/or chemical vapor deposition (CVD), wherein the III-nitride p-n junction includes a first p-type layer, a first n-type layer, and the active region between the first n-type layer and the first p-type layer;
growing a subsequent III-nitride material comprising a second p-type layer and a second n-type layer using MOCVD or chemical vapor deposition (CVD);
forming a mesa in the III-nitride p-n junction and the subsequent III-nitride material;
patterning an array of openings in the subsequent III-nitride material on a top of the mesa through the second n-type layer so to expose the second p-type layer;
reactivating or activating a second p-type layer in the subsequent III-nitride material through lateral and vertical diffusion of hydrogen through the mesa's sidewalls and top surface; and
forming a first metal contact to the first n-type layer and a second metal contact to the second n-type layer,
wherein:
the subsequent III-nitride material forms a tunnel junction at an interface between the second n-type layer and the second p-type layer,
wherein the device comprises a light emitting device outputting light in response to a current density flowing between the first metal contact and the second metal contact.
9 . The method of claim 8 , wherein the first n-type layer in the p-n junction and the active region are grown using the MOCVD, and the first p-type layer, the second p-type layer, and the tunnel junction are grown using the CVD.
10 . The method of claim 8 , wherein delta-doping is used at a regrowth interface between the III-nitride p-n junction and the subsequent III-nitride material.
11 . The method of claim 8 , wherein the subsequent III-nitride material forms layers of III-nitride material and a magnesium (Mg) concentration in the layers of the III-nitride material is suppressed through exposure to an acid or through flow modulation epitaxy.
12 . The method of claim 8 , wherein the reactivating or the activating activates magnesium (Mg) through the lateral and vertical diffusion of hydrogen through the sidewalls and the top surface at an elevated temperature above 800 degrees Celsius.
13 . The method of claim 8 , wherein the activating or the reactivating through the top surface occurs through the openings that expose a surface of the second p-type layer comprising a p-type GaN layer.
14 . The method of claim 8 , wherein a width of the openings is between about 0.1 μm to about 100 μm wide and a spacing between each of the openings is about 0.5 μm to about 400 μm.
15 . The method of claim 8 , wherein the first p-type layer and the second p-type layer comprise p-GaN and the openings are formed before the subsequent III-nitride material including the tunnel junction by first depositing a pattern of a dielectric on a surface of the first p-GaN layer such that the subsequent III-nitride material occurs selectively only on the exposed area of the first p-type layer.
16 . The method of claim 8 , wherein the second n-type layer comprises a pulsed delta n-type doping scheme to realize an abrupt, smoother surface of the second-n-type layer and a higher carrier concentration in the second n-type layer.
17 . The method of claim 8 , wherein delta doping comprising a pulsed delta n-type doping scheme is used at a regrowth interface of the subsequent III-nitride material with the p-n junction or for the entire growth of the subsequent III-nitride material including the tunnel junction.
18 . The method of claim 17 , wherein the pulsed delta n-type doping scheme is achieved by injecting a precursor containing n-type dopant for 40 seconds or less per cycle and forms a continuous layer growth by keeping the precursors comprising Group V and Group III precursors uninterrupted.
19 . The device of claim 1 , wherein:
the light emitting device outputs light with a power of at least 3 mW in response to a current density of at least 10 A/cm 2 flowing between the first metal contact and the second metal contact, and
the current density of at least 5 A/cm 2 flows in response to a voltage of less than 3.5 V applied across the device between the first metal contact and the second metal contact.
20 . The method of claim 8 , wherein the light emitting device outputs light with a power of at least 3 mW in response to a current density of at least 10 A/cm 2 flowing between the first metal contact and the second metal contact, and the current density of at least 5 A/cm 2 flows in response to a voltage of less than 3.5 V applied across the device between the first metal contact and the second metal contact.