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Full-Text Articles in Engineering
Si3N4/Algan/Gan-Metal-Insulator-Semiconductor Heterostructure Field-Effect Transistors, X. Hu, A. Koudymov, Grigory Simin, J. Yang, M. Asif Khan, A. Tarakji, M. S. Shur, R. Gaska
Si3N4/Algan/Gan-Metal-Insulator-Semiconductor Heterostructure Field-Effect Transistors, X. Hu, A. Koudymov, Grigory Simin, J. Yang, M. Asif Khan, A. Tarakji, M. S. Shur, R. Gaska
Faculty Publications
We report on a metal–insulator–semiconductor heterostructurefield-effect transistor (MISHFET) using Si3N4 film simultaneously for channel passivation and as a gate insulator. This design results in increased radio-frequency (rf) powers by reduction of the current collapse and it reduces the gate leakage currents by four orders of magnitude. A MISHFET room temperature gate current of about 90 pA/mm increases to only 1000 pA/mm at ambient temperature as high as 300 °C. Pulsed measurements show that unlike metal–oxide–semiconductor HFETs and regular HFETs, in a Si3N4 MISHFET, the gate voltage amplitude required for current collapse is much higher …
Very-Low-Specific-Resistance Pd/Ag/Au/Ti/Au Alloyed Ohmic Contact To P Gan For High-Current Devices, V. Adivarahan, A. Lunev, M. Asif Khan, J. Yang, Grigory Simin, M. S. Shur, R. Gaska
Very-Low-Specific-Resistance Pd/Ag/Au/Ti/Au Alloyed Ohmic Contact To P Gan For High-Current Devices, V. Adivarahan, A. Lunev, M. Asif Khan, J. Yang, Grigory Simin, M. S. Shur, R. Gaska
Faculty Publications
We report on Pd/Ag/Au/Ti/Au alloyed metallic contact to pGaN. An 800 °C anneal for 1 min in flowing nitrogen ambient produces an excellent ohmic contact with a specific contact resistivity close to 1×10−6 Ω cm2 and with good stability under high current operation conditions. This high-temperature anneal forms an alloy between Ag,Au, and pGaN resulting in a highly p-doped region at the interface. Using x-ray photoelectron spectroscopy and x-ray diffractionanalysis, we confirm that the contact formation mechanism is the metal intermixing and alloying with the semiconductor.
Mechanism Of Radio-Frequency Current Collapse In Gan-Algan Field-Effect Transistors, A. Tarakji, Grigory Simin, N. Ilinskaya, X. Hu, A. Kumar, A. Koudymov, J. Yang, M. Asif Khan, M. S. Shur, R. Gaska
Mechanism Of Radio-Frequency Current Collapse In Gan-Algan Field-Effect Transistors, A. Tarakji, Grigory Simin, N. Ilinskaya, X. Hu, A. Kumar, A. Koudymov, J. Yang, M. Asif Khan, M. S. Shur, R. Gaska
Faculty Publications
The mechanism of radio-frequency current collapse in GaN–AlGaN heterojunctionfield-effect transistors(HFETs) was investigated using a comparative study of HFET and metal–oxide–semiconductor HFET current–voltage (I–V) and transfer characteristics under dc and short-pulsed voltage biasing. Significant current collapse occurs when the gate voltage is pulsed, whereas under drain pulsing the I–V curves are close to those in steady-state conditions. Contrary to previous reports, we conclude that the transverse electric field across the wide-band-gap barrier layer separating the gate and the channel rather than the gate or surface leakage currents or high-field effects in the gate–drain spacing is responsible for the current collapse. We …
Highly Doped Thin-Channel Gan-Metal-Semiconductor Field-Effect Transistors, R. Gaska, M. S. Shur, X. Hu, J. W. Yang, A. Tarakji, Grigory Simin, A. Khan, J. Deng, T. Werner, S. Rumyantsev, N. Pala
Highly Doped Thin-Channel Gan-Metal-Semiconductor Field-Effect Transistors, R. Gaska, M. S. Shur, X. Hu, J. W. Yang, A. Tarakji, Grigory Simin, A. Khan, J. Deng, T. Werner, S. Rumyantsev, N. Pala
Faculty Publications
We report on the influence of the channel doping on dc, high frequency, and noise performance of GaN metal–semiconductor field-effect transistors (MESFETs) grown on sapphire substrates. The devices with the channel thicknesses from 50 to 70 nm and doping levels up to 1.5×1018 cm−3 were investigated. An increase in the channel doping results in the improved dc characteristics, higher cutoff, and maximum oscillation frequencies, and reduced low frequency and microwave noise. The obtained results demonstrate that the dc and microwave performance characteristics of short-channel GaN MESFETs may be comparable to those for conventional AlGaN/GaN heterostructure FETs.