SEMICONDUCTOR OPTICAL DEVICE WITH A BURIED HETEROSTRUCTURE (BH) HAVING REDUCED PARASITIC CAPACITANCE AND REDUCED INTER-DIFFUSION
A semiconductor optical device including a buried heterostructure (BH) has reduced parasitic capacitance and reduced inter-diffusion. The semiconductor optical device is manufactured by a regrowth on both sides of a mesa structure with an Fe-doped current blocking layer and an n-type cladding layer outside of an active region in the mesa structure. The Fe-doped current blocking layer and the n-type cladding layer may be disposed and configured such that Fe/Zn inter-diffusion is reduced or prevented by minimal contact between the Fe-doped current blocking layer and a highly Zn-doped cladding layer and by the n-type cladding layer, as will be described in greater detail below. A low Zn-doped or undoped material may be used for a thin cladding layer above the active region in the mesa structure to further suppress Zn/Fe inter-diffusion.
1 . A semiconductor optical device, comprising:
a semiconductor substrate;
a buried mesa structure formed on the semiconductor substrate, the buried mesa structure including a first n-type cladding layer, an active region above the first n-type cladding layer, and a first p-type cladding layer above the active region;
stacked side layers on each side of the buried mesa structure, the stacked side layers including an Fe-doped current blocking layer burying the buried mesa structure on each side and a second n-type cladding layer on the Fe-doped current blocking layer;
a second p-type cladding layer above the mesa structure and the stacked side layers, wherein the second p-type cladding layer is a highly Zn-doped layer, wherein contact portions of the Fe-doped current blocking layer extend above the active region to contact the highly Zn-doped layer, and wherein the second n-type cladding layer is outside the contact portions of the Fe-doped current blocking layer and between a substantial portion of the Fe-doped current blocking layer and the highly Zn-doped layer.
2 . The semiconductor optical device of claim 1 , wherein the contact portions of the Fe-doped current blocking layer contact the highly Zn-doped layer at a contact region that is less than 5% of the total surface area of the highly Zn-doped layer.
3 . The semiconductor optical device of claim 1 , wherein the contact portions of the Fe-doped current blocking layer taper to a tip that contacts the highly Zn-doped layer.
4 . The semiconductor optical device of claim 1 , wherein the first n-type cladding layer, the second n-type cladding layer, the first p-type cladding layer, and the second p-type cladding layer, and the Fe-doped current blocking layer are InP layers.
5 . The semiconductor optical device of claim 4 , wherein the first p-type cladding layer is a low Zn-doped InP layer.
6 . The semiconductor optical device of claim 5 , wherein the low Zn-doped InP layer has a Zn concentration in a range of 1×10 16 cm −3 to 5×10 17 cm −3 .
7 . The semiconductor optical device of claim 4 , wherein the first p-type cladding layer is an undoped InP layer.
8 . The semiconductor optical device of claim 4 , wherein the second n-type cladding layer is an Si-doped InP layer.
9 . The semiconductor optical device of claim 1 , further including a third p-type cladding layer on the second p-type cladding layer, wherein the third p-type cladding layer is a Zn-doped cladding layer.
10 . The semiconductor optical device of claim 9 , wherein the third p-type cladding layer is a Zn-doped InGaAs layer.
11 . The semiconductor optical device of claim 1 , wherein the active region is a multiple quantum well (MQW) active region.
12 . The semiconductor optical device of claim 11 , further comprising a grating disposed within the first n-type cladding layer below the MQW active region.
13 . The semiconductor optical device of claim 1 , further comprising an n-type metal layer on the bottom under the substrate and a p-type metal layer on the top.
14 . The semiconductor optical device of claim 13 , wherein a top mesa structure is formed by at least the p-type cladding layers and the second n-type cladding layer, and wherein the p-type metal layer is located in a contact window formed on the top mesa structure.
15 . A semiconductor laser, comprising:
a semiconductor substrate;
a buried mesa structure formed on the semiconductor substrate, the buried mesa structure including a first n-type InP cladding layer, an active region above the first n-type InP cladding layer, a grating disposed within the first n-type InP cladding layer below the active region, and a first p-type InP cladding layer above the active region;
stacked side layers on each side of the buried mesa structure, the stacked side layers including an Fe-doped InP layer burying the buried mesa structure on each side and a second n-type InP cladding layer on the Fe-doped InP layer;
a second p-type InP cladding layer above the mesa structure and the stacked side layers, wherein the second p-type cladding layer is a highly Zn-doped InP layer, wherein contact portions of the Fe-doped InP layer extend above the active region to contact the highly Zn-doped InP layer, and wherein the second n-type InP cladding layer is outside the contact portions of the Fe-doped InP layer and between a substantial portion of the Fe-doped InP layer and the highly Zn-doped InP layer; and
a third p-type cladding layer on the second p-type cladding layer, wherein the third p-type cladding layer is a Zn-doped InGaAs layer.
16 . The semiconductor laser of claim 15 , wherein the active region is a multiple quantum well (MQW) active region.
17 . The semiconductor laser of claim 15 , wherein the first p-type cladding layer is a low Zn-doped InP layer or an undoped InP layer.
18 . A semiconductor optical modulator, comprising:
a semiconductor substrate;
a buried mesa structure formed on the semiconductor substrate, the buried mesa structure including a first n-type InP cladding layer, an active region above the first n-type InP cladding layer, and a first p-type InP cladding layer above the active region;
stacked side layers on each side of the buried mesa structure, the stacked side layers including an Fe-doped InP layer burying the buried mesa structure on each side and a second n-type InP cladding layer on the Fe-doped InP layer;
a second p-type InP cladding layer above the mesa structure and the stacked side layers, wherein the second p-type InP cladding layer is a highly Zn-doped InP layer, wherein contact portions of the Fe-doped InP layer extend above the active region to contact the second p-type InP cladding layer, and wherein the second n-type InP cladding layer is outside the contact portions of the Fe-doped InP layer and between a substantial portion of the Fe-doped InP layer and the highly Zn-doped InP layer;
including a third p-type cladding layer on the second p-type cladding layer, wherein the third p-type cladding layer is a Zn-doped InGaAs layer;
wherein a top mesa structure is formed by at least the p-type cladding layers and the second n-type cladding layer;
an n-type metal layer on the bottom under the substrate and a p-type metal layer on the top and located in a contact window formed on the top mesa structure.
19 . The semiconductor optical modulator of claim 18 , wherein the active region is a multiple quantum well (MQW) active region.
20 . The semiconductor optical modulator of claim 18 , wherein the first p-type InP cladding layer is a low Zn-doped InP layer or an undoped InP layer.