Noise temperature of an NbN hot-electron bolometric mixer at frequencies from 0.7 THz to 5.2 THz

We report on noise temperature measurements of an NbN phonon-cooled hot-ele ctron bolometric mixer in the terahertz frequency range. The devices were 3 nm thick films with in-plane dimensions 1.7 x 0.2 mu m(2) and 0.9 x 0.2 mu m(2) integrated in a complementary logarithmic-spiral antenna. Measurement s were performed at seven frequencies ranging from 0.7 THz to 5.2 THz. The measured DSB noise temperatures are 1500 K (0.7 THz), 2200 K (1.4 THz), 260 0 K (1.6 THz), 2900 K (2.5 THz), 4000 K (3.1 THz), 5600 K (4.3 THz) and 880 0 K (5.2 THz).