Group III nitride semiconductor device, and method for fabricating group III nitride semiconductor device
In a group III nitride semiconductor device according to one aspect of the present invention, in a p-type group III nitride semiconductor region formed on a semi-polar plane substrate, the concentration of hydrogen (H) contained in the p-type group III nitride semiconductor region is 25% or less of the concentration of a p-type dopant therein, and the concentration of oxygen contained in the p-type group III nitride semiconductor region is 5×10 17 atoms/cm 3 or lower, and an angle between a normal axis of a primary surface of the semi-polar plane substrate and a c-axis of the semi-polar plane substrate is not lower than 45 degrees and not higher than 80 degrees or not lower than 100 degrees and not higher than 135 degrees in a waveguide axis direction of the group III nitride semiconductor device.
1. A method for fabricating a group III nitride semiconductor device, comprising the steps of:
growing a low hydrogen content film on a semiconductor region including a group III nitride semiconductor layer, the group III nitride semiconductor layer including a p-type dopant, the low hydrogen content film being made of a material different from a group III nitride, the low hydrogen content film having a hydrogen concentration of 1×10 20 cm −3 or lower, an angle between a normal axis of a primary surface of a semi-polar plane substrate and a c-axis of the semi-polar plane substrate is not lower than 45 degrees and not higher than 80 degrees or not lower than 100 degrees and not higher than 135 degrees in a waveguide axis direction of the group III nitride semiconductor device; and
carrying out activation annealing of the semiconductor region to form a p-type group III nitride semiconductor layer from the group III nitride semiconductor layer, after growing the low hydrogen content film.
2. The method according to claim 1 , wherein the step of growing a low hydrogen content film includes growing the low hydrogen content film in a film formation apparatus without using a substance containing hydrogen.
3. The method according to claim 1 , wherein the activation annealing is carried out at a temperature of 600 degrees Celsius or higher.
4. The method according to claim 1 , wherein the low hydrogen content film includes a dielectric body.
5. The method according to claim 4 , wherein the low hydrogen content film comprises at least one of a silicon oxide, a zirconium oxide, an aluminum oxide, a titanium oxide or a tantalum oxide.
6. The method according to claim 1 , wherein the low hydrogen content film includes a metal with hydrogen storage properties.
7. The method according to claim 6 , wherein the low hydrogen content film contains at least one of titanium (Ti), palladium (Pd), nickel (Ni), cobalt (Co), platinum (Pt) or rhodium (Rh).
8. The method according to claim 1 , wherein the low hydrogen content film is formed by a vapor phase growth method.
9. The method according to claim 1 , wherein the low hydrogen content film is formed by an evaporation method.
10. The method according to claim 1 , wherein the low hydrogen content film is formed by an electron beam vapor deposition method.
11. The method according to claim 1 , further comprising a step of, after the step of forming the p-type group III nitride semiconductor layer, removing the low hydrogen content film on the surface of the semiconductor region to expose the p-type group III nitride semiconductor layer.
12. The method according to claim 1 , further comprising a step of, after the step of forming the p-type group III nitride semiconductor layer, processing the p-type group III nitride semiconductor layer so as to form a ridge structure,
wherein the ridge structure extends along a reference plane defined by the c-axis and one of m- and a-axes of the substrate.
13. The method according to claim 1 , wherein the group III nitride semiconductor layer comprises at least one of a Mg-doped GaN layer, a Mg-doped AlN layer, a Mg-doped InN layer, a Mg-doped AlGaN layer, a Mg-doped InGaN layer, a Mg-doped InAlGaN layer or a Mg-doped InAlN layer.