PT Unknown
AU Antipov, S
   Trifonov, A
   Krause, S
   Meledin, D
   Desmaris, V
   Belitsky, V
   Gol’tsman, G
TI Gain bandwidth of NbN HEB mixers on GaN buffer layer operating at 2 THz local oscillator frequency
SE Proc. 28[super:th] Int. Symp. Space Terahertz Technol.
PY 2017
BP 147
EP 148
DE NbN HEB mixers; GaN buffer-layer; IF bandwidth
AB In this paper, we present IF bandwidth measurement results of NbN HEB mixers, which are employing NbN thin films grown on a GaN buffer-layer. The HEB mixers were operated in the heterodyne regime at a bath temperature of approximately 4.5 K and with a local oscillator operating at a frequency of 2 THz. A quantum cascade laser served as the local oscillator and a reference synthesizer based on a BWO generator (130-160 GHz) and a semiconductor superlattice (SSL) frequency multiplier was used as a signal source. By changing the LO frequency it was possible to record the IF response or gain bandwidth of the HEB with a spectrum analyzer at the operation point, which yielded lowest noise temperature. The gain bandwidth that was recorded in the heterodyne regime at 2 THz amounts to approximately 5 GHz and coincides well with a measurement that has been performed at elevated bath temperatures and lower LO frequency of 140 GHz. These findings strongly support that by using a GaN buffer-layer the phonon escape time of NbN HEBs can be significantly lower as compared to e.g. Si substrate, thus, providing higher gain bandwidth.
ER