Crystal laminate, semiconductor device and method for manufacturing the same

1. A crystal laminate comprising:

a crystal substrate formed from a monocrystal of group III nitride expressed by a compositional formula In x Al y Ga 1-x-y N (where 0≤x≤1, 0≤y≤1, 0≤x+y≤1), the crystal substrate containing at least any one of n-type impurity selected from the group consisting of Si, Ge, and O; and

a crystal layer formed by a group III nitride crystal epitaxially grown on a main surface of the crystal substrate, the crystal layer containing at least any one of p-type impurity selected from the group consisting of C, Mg, Fe, Be, Zn, V, and Sb, wherein a concentration of B in the crystal substrate is lower than 1×10 15 at ·cm −3 , and

the crystal laminate is configured in a manner such that an absorption coefficient of the crystal substrate for light with a wavelength of 2000 nm when the crystal substrate is irradiated with the light falls within a range of 1.8 cm −1 or more and 4.6 cm −1 or less under a temperature condition of normal temperature.

2. The crystal laminate of claim 1 , wherein

density of an intrinsic carrier within the crystal substrate is lower than 1×10 17 cm −3 at least under a temperature condition of normal temperature or higher and 1250° C. or lower.

3. The crystal laminate of claim 2 , wherein

concentration of a free electron occurring within the crystal substrate due to addition of the n-type impurity is 1×10 18 cm −3 or more and 2.5×10 18 cm −3 or less under a temperature condition of normal temperature.

4. The crystal laminate of claim 2 , wherein

concentration of the n-type impurity in the crystal substrate is 1×10 18 at·cm −3 or more and 2.5×10 18 at·cm −3 or less.

5. The crystal laminate of claim 2 , wherein

concentration of O in the crystal substrate is 1×10 17 at·cm −3 or less and total concentration of Si and Ge in the crystal substrate is 1×10 18 at·cm −3 or more and 2.5×10 18 at·cm −3 or less.

6. The crystal laminate of claim 1 , wherein

concentration of a free electron occurring within the crystal substrate due to addition of the n-type impurity is 1×10 18 cm −3 or more and 2.5×10 18 cm −3 or less under a temperature condition of normal temperature.

7. The crystal laminate of claim 6 , wherein

concentration of the n-type impurity in the crystal substrate is 1×10 18 at·cm −3 or more and 2.5×10 18 at·cm −3 or less.

8. The crystal laminate of claim 6 , wherein

concentration of O in the crystal substrate is 1×10 17 at·cm −3 or less and total concentration of Si and Ge in the crystal substrate is 1×10 18 at·cm −3 or more and 2.5×10 18 at·cm −3 or less.

9. The crystal laminate of claim 1 , wherein

concentration of the n-type impurity in the crystal substrate is 1×10 18 at·cm −3 or more and 2.5×10 18 at·cm −3 or less.

10. The crystal laminate of claim 9 , wherein

concentration of O in the crystal substrate is 1×10 17 at·cm −3 or less and total concentration of Si and Ge in the crystal substrate is 1×10 18 at·cm −3 or more and 2.5×10 18 at·cm −3 or less.

11. The crystal laminate of claim 1 , wherein

concentration of O in the crystal substrate is 1×10 17 at·cm −3 or less and total concentration of Si and Ge in the crystal substrate is 1×10 18 at·cm −3 or more and 2.5×10 18 at·cm −3 or less.

12. A semiconductor device comprising:

a crystal substrate formed from a monocrystal of group III nitride expressed by a compositional formula In x Al y Ga 1-x-y N (where 0≤x≤1, 0≤y≤1, 0≤x+y≤1), the crystal substrate containing at least any one of n-type impurity selected from the group consisting of Si, Ge, and O; and

a crystal layer formed by a group III nitride crystal epitaxially grown on a main surface of the crystal substrate, the crystal layer containing at least any one of p-type impurity selected from the group consisting of C, Mg, Fe, Be, Zn, V, and Sb, wherein a concentration of B in the crystal substrate is lower than 1×10 15 at·cm −3 , and

the semiconductor device is configured in a manner such that an absorption coefficient of the crystal substrate for light with a wavelength of 2000 nm when the crystal substrate is irradiated with the light falls within a range of 1.8 cm −1 or more and 4.6 cm −1 or less under a temperature condition of normal temperature.

13. A semiconductor device manufacturing method comprising:

preparing a crystal laminate comprising a crystal substrate formed from a monocrystal of group III nitride expressed by a compositional formula In x Al y Ga 1-x-y N (where 0≤x≤1, 0≤y≤1, 0≤x+y≤1), the crystal substrate containing at least any one of n-type impurity selected from the group consisting of Si, Ge, and O, and a crystal layer formed by a group III nitride crystal epitaxially grown on a main surface of the crystal substrate, wherein a concentration of B in the crystal substate is lower than 1+10 15 at·cm −3 , and an absorption coefficient of the crystal substrate for light with a wavelength of 2000 nm when the crystal substrate is irradiated with the light is 1.8 cm −1 or more and 4.6 cm −1 or less under a temperature condition of normal temperature;

ion-implanting at least any one of p-type impurity selected from the group consisting of C, Mg, Fe, Be, Zn, V, and Sb in a main surface of the crystal layer; and

heating the crystal laminate by irradiating the crystal laminate with an infrared ray.

14. The semiconductor device manufacturing method of claim 13 , wherein

the heating of the crystal laminate is performed in a condition in which a support-receiving surface of the crystal laminate is being supported at three or more locations and the crystal laminate and a retaining plate present on the support-receiving surface side of the crystal laminate are separate from each other.

15. The semiconductor device manufacturing method of claim 13 , wherein

the preparation of the crystal laminate includes a crystal growth process of loading a seed crystal substrate and a raw material including a group III element in a reaction vessel, and supplying a nitriding agent and a halide of the raw material onto the seed crystal substrate heated to a predetermined crystal growth temperature to grow a crystal of a nitride of the group III element on the seed crystal substrate, and

in the crystal growth process,

a member formed from a material in which at least a surface of the material does not contain quartz and boron is used as a member defining a high-temperature region, at least, of the reaction vessel, the high-temperature region being a region that is heated to the crystal growth temperature and that comes into contact with gas being supplied onto the seed crystal substrate.