Realization of unexplored frequency terahertz quantum-cascade lasers by using III nitride semiconductors

III Nitride semiconductor is a material having a potential for realizing wide frequency range of quantum cascade lasers (QCLs) including unexplored frequency from 5 to 12 THz. We fabricated GaN/AlGaN THz-QCLs with novel pure-3-level design active regions and achieved lasing at frequency between 5.4-7 THz.