AlGaN/GaN-heterojunction FET with inverted 2DEG Channel

Novel heterojunction AlGaN/GaN-FET with inverted device channel is investigated.FET-heterostructures were grown by MBE on sapphire substrates. Devices were fabricated with 0,25 µ T-shaped gates,using electron beam lithography.Electron density profile under the device gate has demonstrated localization of electrons in very narrow nm-region (1A/mm,and good extrinsic transconductance gm ext ≅140mS/mm.DC - specific output power of HEMT was 2,0W/mm.Extrinsic cut off frequency f τ ext of HEMT,determined from transconductance gm and gate-source capacitance Cgs, was 20GHz.Its intrinsic value,f τ ext ,was found to be as high as 36GHz

Absorption saturation properties and laser Q-switch performance of Cr5+-doped YVO4 crystal

The ground-state and excited-state absorption cross sections of a Cr5+:YVO4 single crystal were determined by the intensity-dependant transmission measurements to be(2.0±0.4)×10-18 cm2 and less than 0.1×10-18 cm2 at 1.08 μm, respectively. The bleaching relaxation time of the Cr5+:YVO4 crystal was estimated to be 3.5±1.5 ns. Passive Q-switching of a diode-pumped Yb3+:YVO4 laser with the Cr5+:YVO4 saturable absorber was realized