| CPC C30B 29/406 (2013.01) [C01B 21/0632 (2013.01); G01N 21/95 (2013.01); H01L 21/02389 (2013.01); C01P 2002/82 (2013.01); C01P 2006/40 (2013.01); C30B 25/02 (2013.01); G01N 2021/8477 (2013.01)] | 5 Claims |
|
1. A GaN free-standing substrate comprising GaN single crystal, containing n-type impurities, with an absorption coefficient α being approximated by equation (1) by a method of least squares in a wavelength range of at least 1 μm or more and 3.3 μm or less:
 where 1.5×10−19≤K≤6.0×10−19, a=3,
a wavelength being λ(μm), an absorption coefficient of the GaN free-standing substrate at 27° C. being α(cm−1), a carrier concentration in the GaN free-standing substrate being Ne (cm−3), and K and a being constants,
wherein an error of an actually measured absorption coefficient with respect to the absorption coefficient α obtained from equation (1) at a wavelength of 2 μm is within ±0.1α, and
in a reflection spectrum measured by irradiating the GaN free-standing substrate with infrared light, there is a peak within a wavenumber range of 1,200 cm−1 or more and 1,500 cm−1 or less, and a peak height which is a difference between an intensity reflectance of the peak and an intensity reflectance of a baseline of the reflection spectrum is 35% or less, the baseline of the reflection spectrum is a reflection spectrum in a case where there is no point defect in the GaN free-standing substrate.
|