Group III nitride light emitting diode with an electron blocking structure
A light emitting diode has a substrate, a group III nitride layer over the substrate for electron supply and n-type ohmic contact formation and a light-emitting multiple-quantum well active region over the group III nitride layer. An electron blocking layer is over the light-emitting multiple-quantum well active region, the electron blocking layer has a periodic structure made of a Al x Ga 1−x N barrier layer and a Al y Ga 1−y N well layer and a laminate comprising an Al x′ Ga 1−x′ N layer of thickness b1, an Al-composition downgraded Al z′ Ga 1−z′ N layer of thickness b, and an Al y′ Ga 1−y′ N layer of thickness b3, where b is greater than each of b1 and b3. A p-contact layer is positioned above the electron blocking layer and a p-contact pad is positioned above the p-contact layer.
1 . A light emitting diode, comprising:
a substrate;
a group III nitride layer over the substrate for electron supply and n-type ohmic contact formation;
a light-emitting multiple-quantum well active region over the group III nitride layer;
an electron blocking layer over the light-emitting multiple-quantum well active region, the electron blocking layer having a first surface proximate to the light-emitting multiple-quantum well active region and a second surface distal to the light-emitting multiple-quantum well active region, the first surface having a bandgap larger than a bandgap of the light-emitting multiple-quantum well active region to suppress electron overflow and the second surface being proximate to a hole accumulation potential well for reduced hole injection barriers to promote lateral hole current;
a p-contact layer positioned above the electron blocking layer; and
a p-contact pad positioned above the p-contact layer;
wherein the electron blocking layer comprises:
a periodic structure made of an Al x Ga 1−x N barrier layer and an Al y Ga 1−y N well layer; and
a laminate comprising an Al x′ Ga 1−x′ N layer of thickness b1, an Al-composition downgraded Al z′ Ga 1−z′ N layer of thickness b, and an Al y′ Ga 1−y′ N layer of thickness b3, where b is greater than each of b1 and b3;
where y and y′∈[0.4, 0.7], x and x′∈[0.45, 1.0], x>y, x′>y′, and z′ decreases from x′ to y′ along the direction pointing from the Al x′ Ga 1−x′ N layer to the Al y′ Ga 1−y′ N layer.
2 . The light emitting diode of claim 1 , where the thicknesses of the Al x Ga 1−x N barrier layer and Al y Ga 1−y N well layer are each less than 3 nm.
3 . The light emitting diode of claim 1 , where the thicknesses of the Al x Ga 1−x N barrier layer and Al y Ga 1−y N well layer are each less than 2 nm.
4 . The light emitting diode of claim 1 , where the thicknesses of the Al x Ga 1−x N barrier layer and Al y Ga 1−y N well layer are each less than 1 nm.
5 . The light emitting diode of claim 1 , where b is in the range of 3-10 nm, b1 and b3 are each in the range of 0-6 nm.
6 . The light emitting diode of claim 1 , where the electron blocking layer has a periodic structure with 0-10 periods, and the laminate repeats 1-10 times.
7 . The light emitting diode of claim 1 wherein the electron blocking layer has a higher Al composition than the light-emitting multiple-quantum well active region.
8 . The light emitting diode of claim 1 further comprising an AlN template positioned over the substrate.
9 . The light emitting diode of claim 8 further comprising a strain management structure positioned over the AlN template.