J. Łusakowski

Room-temperature terahertz emission from nanometer field-effect transistors

Generation of THz radiation in nanometer gate length InAlAs/InGaAs and AlGaN/GaN high mobility transistors is observed at room temperature. Spectral analysis of the emitted radiation is presented.

Magnetoresistance characterization of nanometer si metal-oxide-semiconductor transistors

We report on the high-field (up to 10T) magnetoresistance measurements performed on the short (down to 75-nm gate length) n-type Si metal-oxide-semiconductor field-effect transistors. The electron magnetoresistance mobility of these nanometer devices was determined for a wide range of the electron concentration (107–1013cm−2, i.e., from a weak to a strong inversion) and gate length (10μm–75nm). In the case of long samples, the magnetoresistance mobility was compared to the effective mobility obtained by the standard parameter extraction and the split C–V techniques. The results are discussed in terms of the scattering power-law two-dimensional transport analysis. The data clearly indicate a significant decrease of the mobility with the gate length reduction below 100nm.

Ballistic and pocket limitations of mobility in nanometer Si metal-oxide semiconductor field-effect transistors

Room-temperature magnetoresistance of nanometer bulk Si n-type metal-oxide semiconductor field-effect transistors was measured at magnetic fields up to 10 T. The electron magnetoresistance mobility was determined for transistors with the gate length in 30 to 740 nm range and was shown to decrease with decreasing the gate length. We show that the mobility reduction is caused both by the ballistic and the pocket effect and that for the strong inversion these two effects are of a comparable magnitude.

Quasiballistic transport in nanometer Si metal-oxide-semiconductor field-effect transistors : Experimental and Monte Carlo analysis

Room temperature electron mobility (μ) in nanometer Si metal-oxide-semiconductor field-effect transistors (MOSFETs) with gate length (LG) down to 30 nm was determined by the magnetoresistance method. A decrease of μ with the decrease of LG was observed. Monte Carlo simulations of electron transport in nanometer MOSFETs were carried out for realistic devices as a function of LG. The dependence with LG and electron concentration of simulated mobility and transmission coefficient agree with experimental data. An analysis of scattering events and time of flight gives evidence of the presence of ballistic motion in the investigated structures and proves its influence on mobility degradation in short transistors. The results give arguments that interpretation of the magnetoresistance coefficient as the square of the mobility is valid also in the case of quasiballistic electron transport.

Low electron mobility of field-effect transistor determined by modulated magnetoresistance

Room temperature magnetotransport experiments were carried out on field-effect transistors in magnetic fields up to 10 T. It is shown that measurements of the transistor magnetoresistance and its first derivative with respect to the gate voltage allow the derivation of the electron mobility in the gated part of the transistor channel, while the access/contact resistances and the transistor gate length need not be known. We demonstrate the potential of this method using GaN and Si field-effect transistors and discuss its importance for mobility measurements in transistors with nanometer gate length.

Low temperature electron mobility and concentration under the gate of AlGaN/GaN field effect transistors

High electron mobility field effect transistors were fabricated on AlGaN∕GaN heterostructures and their magnetoresistance was measured at 4.2K up to 10T with simultaneous modulation of the gate potential. Low and high magnetic field data were used to determine the electron mobility (μ) and concentration (n), respectively, in the gated part of the transistor channel. With these measurements we present a method to determine μ and n under the gate of a transistor, which does not require knowledge of the transistor gate length, access resistance, threshold voltage, or capacitance. We discuss applications of this method for nanometer and ballistic transistors.

TeraHertz Emission and Noise Spectra in HEMTs

In this work we investigate, by means of Monte Carlo simulations, the physics of the recently observed emission of THz radiation at low temperature (4.2 K) from InGaAs/InAlAs lattice‐matched high electron mobility transistors, HEMTs. The spectrum of the emitted signal consists of two maxima; the one at lower frequency (around 1 THz) is sensitive to UDS and UGS, while the higher frequency peak (around 5 THz) is not. The gate current noise spectra obtained with room‐temperature Monte Carlo simulations of similar HEMTs also show those features, although some quantitative discrepancies arise from the different temperature conditions. The signature of plasma oscillations is known to appear in the current noise spectrum, producing peaks appearing at very high frequencies. On the other hand, peaks at frequencies around 1 THz can be associated with the formation of Gunn domains within the transistors. Therefore, the analysis of the noise spectra of these devices can provide useful information that can help to und...

Terahertz emission and detection by plasma waves in nanoscale transistors

We report on the detection of the sub‐THz and THz radiation by silicon FETs and on the voltage tunable emission of terahertz radiation from InGaAs/AlInAs HEMTs with nanoscale gate lengths. The observed photo‐response is in agreement with the predictions of the plasma wave response theory. The spectrum of the emitted signal has two peaks. The lower peak is interpreted as resulting from the Dyakonov — Shur instability of the gated two dimensional electron fluid. The emission measurements in a magnetic field show that the threshold voltage remains close to the transistor saturation voltage that increases with magnetic field due to geometric magnetoresistance.