Characterization of AlGaN/GaN-on-Si HFETs in high-power converter applications

AlGaN/GaN-on-Si Heterostructure Field-Effect Transistors (HFETs) for power switching are investigated in this paper. A design study for a fast switching environment for power devices is provided including an analysis of the technology, the fabrication, and the performances of large-area AlGaN/GaN-on-Si HFETs. Different power packages and high-current drivers are compared and the results are being discussed. Furthermore the power conversion efficiency is being evaluated for different power- and switching-frequency ranges by means of a converter test board. At 100 kHz efficiencies up to 98.7 % at power levels of up to 1.6 kW could be achieved. At 1 MHz and 1 kW input power an efficiency of 97.1 % was measured

High-voltage stress time-dependent dispersion effects in AlGaN/GaN HEMTs

In this work we investigate the dispersion effects of GaN based HEMTs as a function of the off-state stress voltage and the stress time. We characterize the reduction of the drain current in on-state after off-state stress time from 2 µs up to 10 s. In addition, we compare different source- and gate-terminated field plate configurations. High-voltage (HV) pulsed stress tests with several stress rates are carried out to measure the increase of dynamic on-resistance over time. A new analytic model is developed to estimate the relevant trapping and detrapping time constants of the devices. By HV pulsed stress tests at different temperatures it is possible to estimate the activation energies for both processes

Self-starting soliton-modelocked femtosecond Cr(4+):YAG laser using an antiresonant Fabry-Perot saturable absorber

We set up a self-starting passively modelocked femtosecond Cr(4+):YAG laser using a low-finesse antiresonant Fabry-Perot saturable absorber (A-FPSA). Stable transform-limited pulses were produced without the critical cavity alignment necessary for Kerr lens modelocking. We achieved 114-fs pulses with 94 mW output power at the telecommunication wavelength 1.5 mu m. The pulse formation is demonstrated to be due to soliton modelocking. At higher intracavity energy multiple pulsing was observed and is explained by the saturation behaviour of the A-FPSA. In the multipulsing regime a pulse width as short as 95 fs and an averaged output power of up to 395 mW have been obtained

Q- and E-band amplifier MMICs for satellite communication

This work discusses MMICs for the realization of spaceborn multi-Gigabit satellite communication systems. A broadband low-noise amplifier, based on a 50 nm GaAs mHEMT technology, has been developed for Q-band low-noise receivers. The amplifier shows a small-signal gain of 27.5 dB with a gain flatness of ± 1.2 dB and a noise figure below 2 dB over the entire targeted frequency range between 30 and 50 GHz. For the next generation of E-band transmitter modules, a GaN-based highpower amplifier with a small-signal gain above 15 dB between 70-75 GHz and a saturated output power exceeding 28 dBm at 74 GHz has been developed

Monolithische MOPA-Leistungslaserdioden auf GaAs-Substraten fuer hohe optische Ausgangsleistungen Abschlussbericht

Available from TIB Hannover: DtF QN1(62,48) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman