Nitride-semiconductor technologies for blue lasers are reviewed. Nitride semiconductors from GaN to InN are covered with respect to MOVPE growth and characteristics. For GaN, two-step growth significantly improves crystalline characteristics, such as the concentration of residual carriers, mobility, and surface morphology. For InGaN, a key material for the emitting layer of blue lasers, the use of nitrogen as the carrier and bubbling gases for metalorganic sources enhances indium incorporation, and composition control has been achieved. The phase separation of InGaAlN system has been semiempirically predicted using the strictly regular solution model. As substrates for the epitaxial growth, a several materials are discussed along with the affect of the substrate polarity on
the characteristics of epitaxially grown GaN. P- and n-type doping are also briefly examined. Looking at future prospects for blue lasers, the effect of polarization in device structures and the bulk-crystal growth for substrates are described.