High Electron Mobility Field Effect Transistor Research Articles

Deep Ultraviolet Excitation Photoluminescence Characteristics and Correlative Investigation of Al-Rich AlGaN Films on Sapphire.

AlGaN is attractive for fabricating deep ultraviolet (DUV) optoelectronic and electronic devices of light-emitting diodes (LEDs), photodetectors, high-electron-mobility field-effect transistors (HEMTs), etc. We investigated the quality and optical properties of AlxGa1-xN films with high Al fractions (60-87%) grown on sapphire substrates, including AlN nucleation and buffer layers, by metal-organic chemical vapor deposition (MOCVD). They were initially investigated by high-resolution X-ray diffraction (HR-XRD) and Raman scattering (RS). A set of formulas was deduced to precisely determine x(Al) from HR-XRD data. Screw dislocation densities in AlGaN and AlN layers were deduced. DUV (266 nm) excitation RS clearly exhibits AlGaN Raman features far superior to visible RS. The simulation on the AlGaN longitudinal optical (LO) phonon modes determined the carrier concentrations in the AlGaN layers. The spatial correlation model (SCM) analyses on E2(high) modes examined the AlGaN and AlN layer properties. These high-x(Al) AlxGa1-xN films possess large energy gaps Eg in the range of 5.0-5.6 eV and are excited by a DUV 213 nm (5.8 eV) laser for room temperature (RT) photoluminescence (PL) and temperature-dependent photoluminescence (TDPL) studies. The obtained RTPL bands were deconvoluted with two Gaussian bands, indicating cross-bandgap emission, phonon replicas, and variation with x(Al). TDPL spectra at 20-300 K of Al0.87Ga0.13N exhibit the T-dependences of the band-edge luminescence near 5.6 eV and the phonon replicas. According to the Arrhenius fitting diagram of the TDPL spectra, the activation energy (19.6 meV) associated with the luminescence process is acquired. In addition, the combined PL and time-resolved photoluminescence (TRPL) spectroscopic system with DUV 213 nm pulse excitation was applied to measure a typical AlGaN multiple-quantum well (MQW). The RT TRPL decay spectra were obtained at four wavelengths and fitted by two exponentials with fast and slow decay times of ~0.2 ns and 1-2 ns, respectively. Comprehensive studies on these Al-rich AlGaN epi-films and a typical AlGaN MQW are achieved with unique and significant results, which are useful to researchers in the field.

Damage effects and mechanism of the GaN high electron mobility transistor caused by high electromagnetic pulse

As electromagnetic environment of semiconductor device and integrated circuit deteriorates increasingly, electromagnetic pulse (EMP) of device and damage phenomenon have received more and more attention. In this paper, the damage effect and mechanism of the GaN high electron mobility field effect transistor(HEMT) under EMP are investigated. A two-dimensional electro-thermal theoretical model of GaN HEMT under EMP is proposed, which includes GaN polarization effect, mobility degradation in large electric field, avalanche generation effect, and self-heating effect. The internal transient response of AlGaN/ GaN HEMT is analyzed under the EMP injected into the gate electrode, and the damage mechanism is studied. The results show that the temperature of device keeps increasing, and the rate is divided into three stages, which present a tendency of rapid-slow-sharp till burn-out. The first rapid increasing of temperature is caused by the avalanche breakdown, and then rate becomes smaller due to the decrease of electric field. As the temperature is more than 2000 K, a positive feedback is formed between the hot electron emission and temperature of device, which causes temperature to sharply increase till burn-out. The maximum values of electric field and current density are located at the cylinder surface beneath the gate around the source, which is damage prone because of heat accumulation. Finally, the dependences of the EMP damage power, P, and the absorbed energy, E, on pulse width are obtained in a nanosecond range by adopting the data analysis software. It is demonstrated that the damage power threshold decreases but the energy threshold increases slightly with the increasing of pulse-width. The proposed formulas P = 38-0.052 and E = 1.1 0.062 can estimate the HPM pulse-width dependent damage power threshold and energy threshold of AlGaN/GaN HEMT, which can provide a good prediction of device damage and a guiding significance for electromagnetic pulse resistance destruction.

Detection of different target-DNA concentrations with highly sensitive AlGaN/GaN high electron mobility transistors

This paper presents the successful detection of different target-DNA concentrations using AlGaN/GaN high electron mobility field effect transistors (HEMTs). The gate was bio-functionalized with two different densities of complementary DNA before application of target-DNA. Dosages of 10−16 mol/L up to the gate saturation were tested. The DNA concentration was increased by a factor of 10 each time, and the transistor transfer characteristics were measured. The threshold voltage shift and drain–source current change depend on target concentration and obey the Sips adsorption model. The AlGaN/GaN HEMTs are highly sensitive to very low target-DNA concentrations with a detection limit of 10−14mol/L. The gates with a low probe-DNA density were saturated with a lower target-DNA concentration and presented a faster hybridization equilibrium constant.

Sips adsorption model for DNA sensing with AlGaN/GaN high electron mobility transistors

ABSTRACTThis work presents an adsorption model based on the Sips isotherm for sensing different concentrations of DNA with open gate AlGaN/GaN high electron mobility field effect transistors (HEMTs). Probe-DNA was immobilized on the transistor gate before the application of target-DNA. Concentrations of 10-15 to 10-6 mol/L were tested. The sensor has a detection limit of 10-12 mol/L and saturates after the addition of 10-8 mol/L target-DNA.

Mobility spectrum analysis of carrier transport at insulator/semiconductor interfaces

Display Omitted HighlightsMobility spectrum analysis (MSA) is a powerful tool to determine accurate transport parameters.MSA provides information about carrier mobility distributions.High resolution MSA stimulating progress into the modelling carrier mobility distributions. In this work, we review the results of mobility spectrum analysis (MSA) based studies of electronic transport in GaN-based high electron mobility field effect transistor (HEMT) structures, including recent progress in the modelling of mobility distributions and carrier scattering in two-dimensional electron gases in AlGaN/GaN HEMTs. It is shown that the MSA approach can provide crucial information for epitaxial growth process optimisation, since it allows identification of parasitic conduction channels, and can also yield greater insight into the fundamental scattering mechanism and electronic transport phenomena in two-dimensional inversion and accumulation layers. Furthermore, the availability of high quality insulator/semiconductor-like heterostructures, wherefrom high resolution mobility spectra can be obtained, is stimulating progress into the modelling and simulation of carrier mobility spectra and mobility distributions.

Polarization sensitive detection of 100 GHz radiation by high mobility field-effect transistors

Detection of 100 GHz electromagnetic radiation by a GaAs/AlGaAs high electron mobility field-effect transistor was investigated at 300 K as a function of the angle α between the direction of linear polarization of the radiation and the symmetry axis of the transistor. The angular dependence of the detected signal was found to be A0 cos2(α−α0)+C with A0, α0, and C dependent on the electrical polarization of the transistor gate. This dependence is interpreted as due to excitation of two crossed phase-shifted oscillators. A response of the transistor chip (including bonding wires and the substrate) to 100 GHz radiation was numerically simulated. Results of calculations confirmed experimentally observed dependencies and showed that the two oscillators result from an interplay of 100 GHz currents defined by the transistor impedance together with bonding wires and substrate related modes.

Theoretical study of a GaN-AlGaN high electron mobility transistor including a nonlinear polarization model

We present a theoretical model of an AlGaN-GaN high electron mobility field effect transistor (HEMT) that includes a nonlinear model of the strain polarization fields produced at the heterointerface. Recent experimental work has indicated that the macroscopic polarization in III-nitride alloys is a nonlinear function of the material composition. It is well known that the behavior of a GaN-AlGaN HEMT depends greatly upon the properties of the strain-induced polarization fields formed at the GaN-AlGaN heterointerface. It is the purpose of this paper to provide a detailed model of a GaN-AlGaN HEMT that includes a nonlinear formulation of the polarization. The model is found to agree well with recent experimental measurements made for GaN-AlGaN HEMTs when the nonlinear polarization model is included. The cutoff frequency, transconductance, and current-voltage characteristics are computed. The effect of the nonlinear polarization model on the sheet carrier density is also presented.

Low noise, low power consumption high electron mobility transistors amplifier, for temperatures below 1 K

Low noise three-stage pseudomorphic high electron mobility field-effect transistors amplifier were designed for the temperature range below 1 K. A minimum noise temperature TN≈100 mK was measured at an ambient temperature of about 380 mK at frequencies between 1 and 4 MHz for a source resistance of 10 kΩ. The gain of the amplifier was 50 at a power consumption of about 200 μW. The noise parameters of the amplifier are stable to within 30%, for a power consumption in the range of 100–300 μW. Minimum voltage spectral noise density of the amplifier with respect to the input is about 200 pV/Hz1/2 and the corner frequency of the 1/f noise is close to 300 kHz.

Preliminary results from the ROC-Europe transition radiation experiment with a multichannel superheated superconducting grain detector

A compact multichannel Superheated Superconducting Grain detector (SSG) has been irradiated by the T9 beam (mostly composed by high energy electrons) of the SPS machine at CERN. The SSG detector consists of a set of cylindrical suspensions of tin grains with various filling factors, all of them parallel to the beam line and kept in an 3 He– 4 He single-dilution chamber. Transitions to the normal state of the grains were detected with a GaAs high electron mobility field effect transistor (HEMFET) preamplifier cooled to 4.2 K. We present a preliminary analysis of the results obtained with beam energies from 1 to 14 GeV and a 33–37 μm size distribution of the grains.

Degradation of performance in MESFETs and HEMTs: simulation and measurement of reliability

Low noise GaAs based metal semiconductor field effect transistors (MESFETs) and high electron mobility field effect transistors (HEMTs) are subjected to temperature accelerated testing in order to study the degradation mechanism of the tested devices as a function of temperature and time. The major failure modes are found to consist of a decrease in the zero-bias drain-to-source saturation current ( I DSS ) and pinch-off voltage ( V p ), and an increase in series resistance of ohmic contact. A degradation model based on the “gate sinking” and degradation of ohmic contact is proposed to simulate the degradation of I–V characteristics. The proposed model includes the effects of a decrease in effective channel thickness, reduction of free carrier mobility, and compensation of free carrier due to the gate metal penetration into the active channel layer, which results in good agreement between the calculated and experimental results.

Development of accurate on-wafer, cryogenic characterization techniques

Significant advances in the development of high electron mobility field-effect transistors (HEMT's) have resulted in cryogenic, low-noise amplifiers (LNA's) whose noise temperatures are within an order of magnitude of the quantum noise limit (h/spl nu//k). Further advances in HEMT technology at cryogenic temperatures may eventually lead to the replacement of maser and superconducting-insulator-superconducting (SIS) front-ends in the 1-100 GHz frequency band. Key to identification of the best HEMT's and optimization of cryogenic LNA's is accurate and repeatable device measurements at cryogenic temperatures. A cryogenic on-wafer noise and scattering parameter measurement system has been developed to provide a systematic investigation of HEMT noise characteristics. In addition, an improved parameter extraction technique has been developed to help understand the relationship between device structure and LNA performance.

Epitaxial lift-off GaAs HEMT's

An extensive study of epitaxial lift-off (ELO) Al/sub 0.3/Ga/sub 0.7/As/GaAs modulation doped heterostructure high electron mobility field-effect transistors (HEMT's) is presented. Effects of ELO on electron transport properties of two-dimensional electron gas at AlGaAs/GaAs interface are investigated. An ELO HEMT with 1.5 /spl mu/m gate length had a maximum extrinsic transconductance g/sub m-max/=125 mS/mm, a unity current gain cut-off frequency f/sub t/=10.5 GHz, and a maximum frequency of oscillation f/sub max/=12 GHz. Statistical distributions of maximum intrinsic transconductance of ELO HEMT's are presented and compared with their on-wafer counterparts. Stability of the ELO HEMT's has also been evaluated by continuous operation at room temperature under dc bias. >

11 GHz ultrawide-bandwidth monolithic photoreceiverusing InGaAs pin PD and InAlAs/InGaAs HEMTs

A very-wide-bandwidth long-wavelength monolithically integrated photoreceiver is presentad which comprises an InGaAs pin PD and a transimpedance amplifier. The receiver uses epilayers grown by one-step MOVPE. The InGaAs channel high-electron-mobility field effect transistor (HEMT) employs an Si planar-doped carrier supplying layer to obtain larger transconductance and uniform threshold voltage. The 0.5 µm gate length is used for HEMTs to enhance the speed of operation. This receiver shows a very wide bandwidth of 11 GHz, and opened eye for a 15 Gbit/s NRZ signal. This is the first demonstration of a long-wavelength monolithic photoreceiver receiving a 15 Gbit/s light signal.

Extrinsic layer at AlxGa1−xAs-GaAs interfaces

Photoluminescence studies of GaAs-AlxGa1−xAs heterostructures grown by molecular beam epitaxy (MBE) which contain one and two GaAs quantum wells suggest that in some of the samples the first well grown usually exhibits a ’’rough’’ (6 Å≲δL≲15 Å) first interface and an acceptorlike luminescing impurity in the first few tens of angstroms of GaAs grown. The luminescence may arise from carbon which accumulates on the AlxGa1−xAs -vacuum interface during growth and is then deposited in the first few unit cells of GaAs. The phenomenon discussed may be relevant to the problem of growing high electron mobility field-effect transistor heterostructures by MBE with GaAs on the top.