Patent Document 1 (Japanese Patent Application Laid-Open No. 2001-127002) discloses a method of activating a p-type dopant in a semiconductor layer in a GaN semiconductor laser. When laser beam is applied to a nitride-based GROUP III-V compound semiconductor, such as GaN, doped with the p-type dopant Mg to activate the p-type dopant, the laser beam has a photon energy in a range of Eg-real±0.5 eV, where Eg-real, which is an actually measured bandgap of the semiconductor, is a photon energy for which the absorption coefficient “a” of the semiconductor is equal to a quantity defined by “a=1/d”, and “d” is a thickness of the semiconductor in which the dopant is to be activated.
Patent Document 2 (Japanese Patent Application Laid-Open No. 11-224957) discloses that, when a semiconductor layer contains a considerable amount of a group II-element impurity, activation is implemented by applying laser beam of not less than 10 W/cm2 nor more than 500 W/cm2 to the p-type nitride semiconductor layer in which the dopant is not activated. The activation is further promoted if the p-type nitride semiconductor layer is also doped with an n-type dopant.
Patent Document 3 (Japanese Patent Application Laid-Open No. 2000-306854) discloses a method of activating a p-type layer in a gallium nitride (GaN) compound semiconductor device. This method irradiates the p-type layer at a temperature in the range of 200° C. to 500° C. with light containing wavelengths in the range from ultraviolet to visible light, thereby removing hydrogen bound to the p-type dopant in the p-type layer to activate the p-type dopant as an acceptor.
Patent Document 4 (Japanese Patent Application Laid-Open No. 9-266218) discloses a method of forming a p-type II-VI compound semiconductor or GaN compound semiconductor of low-resistance without annealing after crystal growth. The p-type II-VI compound semiconductor or GaN compound semiconductor epitaxially grown by MOCVD is irradiated with pulsed laser beam of the photon energy not less than the bandgap energy of these compound semiconductors to generate electron-hole pairs. Namely, since the pulsed laser beam has the wavelength corresponding to the energy not less than the bandgap energy of the irradiated semiconductor, an electron-hole pair is generated by a single photon. Bonding between the p-type dopant and hydrogen is cut by electric effect of carriers generated from the electron-hole pair, to remove hydrogen from the interior of the p-type compound semiconductor.    Patent Document 1: Japanese Patent Application Laid-Open No. 2001-127002    Patent Document 2: Japanese Patent Application Laid-Open No. 11-224957    Patent Document 3: Japanese Patent Application Laid-Open No. 2000-306854    Patent Document 4: Japanese Patent Application Laid-Open No. 9-266218