Christiane Poblenz

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We report on the fabrication and high-frequency characterization of AlGaN/GaN high-electron mobility transistors (HEMTs) grown by molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). In devices with a gate length of 160 nm, a record power density of 10.5 W/mm with 34% power added efficiency (PAE) has been measured at 40 GHz in(More)
This letter reports AlGaN/GaN high-electron mobility transistors with capless activation annealing of implanted Si for nonalloyed ohmic contacts. Source and drain areas were implanted with an Si dose of 1/spl times/10/sup 16/ cm/sup -2/ and were activated at /spl sim/1260/spl deg/C in a metal-organic chemical vapor deposition system in ammonia and nitrogen(More)
GaN-based enhancement-mode (E-mode) HEMTs are attracting significant interest for integration of control circuitry and for the added safety of a normally-off device in power switching applications. While previous work reports excellent performance by gate-recessing' and Fluorine-based plasma treatment2, the Schottky gate turn-on voltage of these devices are(More)
A selective dry etch technology of GaN over AlGaN using BCl<sub>3</sub>/SF<sub>6</sub> has been applied to passivation-free deep-recessed GaN HEMTs, significantly reducing the effects of growth and process variations on the device performance, improving reproducibility and manufacturability. The effects of Si delta-doping density on the gate leakage,(More)
We report AlGaN-GaN high electron mobility transistors (HEMTs) grown by molecular beam epitaxy (MBE) on SiC substrates with excellent microwave power and efficiency performance. The GaN buffers in these samples were doped with carbon to make them insulating. To reduce gate leakage, a thin silicon nitride film was deposited on the AlGaN surface by chemical(More)
In this letter, unpassivated high power deeply recessed GaN-based high electron mobility transistors (HEMTs) are reported. The introduction of a thick graded AlGaN cap layer and a novel fluorine-plasma surface treatment reduced the gate-leakage current and increased breakdown voltage significantly, enabling the application of much higher drain biases. Due(More)
Development of AIGaN/GaN HEMTs has been largely advanced in recent years, leading to record microwave power performance from solid-state devices. With the AIGaN/GaN HEMTs emerging as a viable technology for high frequency low noise amplifiers and power amplifiers, there are still several problems to be solved. One key problem is the relatively high gate(More)
A study of the effects of traps on the RF characteristics of AlGaN/GaN HEMTs is conducted using small and large-signal microwave measurements with deep-level optical spectroscopy. Different variations of the drain current swing are observed for illuminations of different photon energies. The time evolution of the current swing in transient measurements(More)