Length High Electron Mobility Transistors Research Articles

Demonstration of AlGaN/GaN high-electron-mobility transistors on 100 mm diameter Si(111) by plasma-assisted molecular beam epitaxy

AlGaN/GaN high-electron-mobility transistor structures grown on 100 mm high-resistivity Si(111) substrates using plasma-assisted molecular beam epitaxy are reported. The two-dimensional electron gas (2DEG) formation in the heterostructures was realized by the growth optimization of two-step low temperature and high temperature AlN layers and GaN buffer layer. High-electron mobility of 1100 cm2/V s with a sheet carrier density of 9×1012 cm−2 was achieved. The presence of 2DEG in the AlGaN/GaN interface was confirmed by temperature dependent Hall measurements and capacitance-voltage carrier profiling. The fabricated 1.5 μm gate length high electron mobility transistor exhibited a maximum drain current density of 530 mA/mm and a peak extrinsic transconductance of 156 mS/mm.

Design Aspects of a Submicrometer Gate Length High Electron Mobility Transistor

An optimized model based on the solution of two-dimensional Poissons equation with improved performance for design aspect of a submicron gate length device is proposed. It analyses the dependence of threshold voltage on the process parameters and gives an idea about the choice of the doping concentration and AIGaAs layer thickness to obtain a minimum threshold voltage variation. The model discusses the different short channel parameters with their effect on the subthreshold current. When calculated results from the present model are compared with available experimental aata, a close agreement between the two is observed, thereby, confirming the validity of the model.

Non-isothermal quasi-bidimensional energy balancemodel

The self heating effect in ultrashort gate length high electron mobility transistors (HEMTs) is investigated. An original model is presented which accounts for both bidimensional heat transfer and quasi bidimensional energy balance carrier transport.

W-band six-port network analyzer for two-port characterization of millimeter wave transistors

A W-band (75–100 GHz) six-port network analyzer was constructed from discrete WR-10 waveguide components for the two-port S-parameter characterization of state-of-the-art submicron gate length high electron mobility transistors. The six-port was capable of measuring the phase of a circuit’s reflection or transmission coefficient to within a 6° and the magnitude to within 1.5% for large reflections and to within 10% for small reflections (return loss of 20 dB). A comparison between the six-port and a down-converter-type frequency extender for a conventional network analyzer revealed the superior performance of the six-port. To demonstrate the applicability of the six-port network analyzer to device characterization, the S-parameters of 0.1-μm gate length HEMTs were measured and then used to calculate the maximum available gain achievable with these transistors at W-band frequencies. These measurements indicate the important role the six-port network analyzer will play in the future development of millimeter wave transistors.

Operation of a high-frequency photodiode-HEMT hybrid photoreceiver at 10 GHz

A hybrid photoreceiver based on an ITO/GaAs photodiode integrated with a 0.5 ?m gate length high electron mobility transistor (HEMT) is reported. The receiver gave an 8 dB associated gain at 10 GHz compared with a discrete detector.

Microwave performance of 0.25-µm gate length high electron mobility transistors

The performance of 0.25-µm gate length high electron mobility transistors (HEMT's) is reported. Devices were fabricated on layers grown by MBE. One of the heterostructures had no undoped AlGaAS spacer layer (wafer A), whereas the other had a 40-Å spacer layer (wafer B). The maximum stable gain on both wafers was ∼ 12 dB at 18 GHz. The minimum noise figure measured was 0.60 dB at 8 GHz and 1.3 dB at 18 GHz. Wafer A yielded devices with a unity current gain cutoff frequency f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</inf> of 65 GHz whereas wafer B gave an f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</inf> of 70 GHz. These results can be attributed primarily to the high quality material, low parasitic resistance, and short gate length.

Quarter-micron gate length microwave high electron mobility transistor

Quarter-micron gate length high electron mobility transistors have been fabricated using an electron-beam direct-writing technique. A maximum stable gain of 10 dB at 18 GHz has been measured at room temperature. A room-temperature cutoff frequency fT as high as 45 GHz has also been obtained.