In this paper, the transient analysis of an AlGaN/GaN high-electron mobility transistor (HEMT) device is presented. Drain-current dispersion effects are investigated when gate or drain voltages pulsed. Gate-lag and drain-lag turn-on measurements analyzed, revealing clear mechanisms current collapse related effects. Numerical 2-D simulations considering surface traps in a physical HEMT model have also been carried out. A comparison between experimental theoretical results shown. The presence...

Photocapacitance spectra in undoped, metal-organic vapor-phase-epitaxy-grown GaN layers, a range of photon energies from 0.6 to 3.5 eV, reveal two main persistent features: broad increase the capacitance 2.0 2.5 and steep decrease at 1 only observed after previous light exposure above eV. A deep trap (${\mathrm{E}}_{\mathrm{v}}$ +1 eV) that captures photoelectrons valence band, being emptied with photons is proposed as origin these features. Optical-current deep-level transient spectroscopy...

A model to explain the behaviour of GaN photoconductive detectors is proposed, and it based on idea a volume modulation rather than carrier density modulation. Space charge regions inside semiconductor produce variation conductive when carriers are photogenerated. The strong non-exponential photocurrent decays result from capture processes over barriers associated with space regions. By means computer simulation, this explains quite well current photoconductor devices predicts their time...

GaN photoconductive detectors have been fabricated on sapphire substrates by metal organic vapor phase epitaxy and gas-source molecular beam Si (111) substrates. The photodetectors showed high photoconductor gains, a very nonlinear response with illuminating power, an intrinsic nonexponential photoconductance recovery process. A novel gain mechanism is proposed to explain such results, based modulation of the conductive volume layer.

We report on the characterization of ZnSe- and ZnMgBeSe-based Schottky barrier photodetectors grown semi-insulating GaAs(001) by molecular-beam epitaxy. The spectral response devices shows a very sharp cutoff at variable wavelength, determined alloy composition, with large stop-band rejection. Short-wavelength responsivities 0.10 A/W detectivities as high 1.4×1012 cm Hz1/2 W−1 −3.5 V bias have been achieved. Their time behavior has analyzed in detail. When light is switched off, show...

The properties of deep donor states (DX centers) in III-V alloys are discussed relation to their influence on device characteristics and performance. techniques avoid or minimize such deleterious effects AlGaAs-based devices discussed, along with physical basis, some guidelines for improved design established. New results about the benefits proper selection, role In alloying, advantage δ doping layers modulation-doped devices, use AlInAs InGaP as alternative wide band-gap presented.

Numerical 2D transient simulations of surface trap effects in AlGaN/GaN HEMT and GaN MESFET devices have been performed. The influence donor- acceptor-type traps on drain current characteristics has studied, when the gate voltage is pulsed. Opposite behaviour response mechanism both found. collapse related dispersion are due to traps, acting as electron devices, whereas for donor-type hole origin these effects. Free accumulation top plays a decisive role HEMT. A detailed study about density,...

Any planar resistor (channel) close to a conducting layer left floating (gate) forms capacitor <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> whose thermal voltage noise ( xmlns:xlink="http://www.w3.org/1999/xlink">kT</i> / noise) has backgating effect on the sheet resistance of channel that is powerful source 1/ xmlns:xlink="http://www.w3.org/1999/xlink">f</i> in resistors and, hence, devices. This spectrum created by bias...

We report the fabrication and frequency characterization of mechanical resonators piezoelectrically actuated with aluminum nitride films. The consist a freestanding unimorph structure made up metal/AlN/metal piezoelectric stack Si3N4 supporting layer. show that electrical impedance one-port device can be used to assess vibrational behavior resonators, provided modes do not exhibit specific symmetries, for which variations cancel. Frequency shifts arise when loading small masses. As...

Low frequency noise has been studied in Al0.15Ga0.85N/GaN high electron mobility transistors grown on sapphire substrates by metal organic vapour phase epitaxy. A strong dependence between the Hooge parameter αH and VGS was found. as low 5 × 10-4 obtained at = 0 V. Mobility fluctuations produced changes rate of trapping charge dislocations are suggested to be dominant 1/f mechanism, although screening effects channel electrons significantly reduce their effect properties.

We report an experimental determination of the pyroelectric coefficient for strained InGaAs layers in a pseudomorphic piezoelectric In0.17Ga0.83As/GaAs multiquantum well p-i-n diode configuration which was grown on (111)B GaAs substrate by molecular-beam epitaxy. By analyzing Franz–Keldysh oscillations photoreflectance spectra over temperature range 11–300 K, we obtained dependence field, from variation constant e14 deduced. A linear with observed. Therefore, strain-induced component...

The electrical properties of n-type AlxGa1−x As, for x&amp;gt;0.2, are governed by deep donor states (formerly called DX centers) created the isolated atoms. We have studied capacitance such layers Si and Sn dopants. meanings capacitance-voltage carrier profiling dependence with temperature been considered. energy position respect to Γ minimum has determined.

Two-dimensional simulations of surface charge effects in AlGaN/GaN HEMT and GaN MESFET devices are performed. The influence charges different magnitude, sign spatial distribution at the ungated on drain current characteristics is studied. We have found that positive negative same magnitude produce very modifications current. relative polarization fields, free hole accumulation top considered gives rise to opposite behaviour devices. implications our study collapse related dispersion FETs discussed.

We have recently shown that thermal noise in the space-charge regions of solid-state devices can account for most their excess noise, whose 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> spectrum is produced by DC bias was used to convert resistance into a voltage be measured. This reflects modulation an energy barrier confines carriers along channel such devices-a feature also found electrons around cathodes vacuum tubes. Using this...

This paper shows that today's modelling of electrical noise as coming from noisy resistances is a non sense one contradicting their nature systems bearing an noise. We present new model for including Johnson and Nyquist work also agrees with the Quantum Mechanical description done by Callen Welton, where energy fluctuates dissipated time. By two currents Admittance function links in frequency domain common voltage, this connection Cause-Effect exists between Fluctuation Dissipation time...

Undoped layers of GaN grown by MOVPE on sapphire substrates have been characterized photoluminescence, photocapacitance and photoinduced current transient spectroscopy (PICTS). Photocapacitance reveals in all samples two specific signatures at photon energies 1 eV 2.5 eV. The decrease observed seems to be due an electron capture process from the valence band, whereas capacitance increase is related emission process. fact that step only seen after photoionization above eV, correlation between...

In this work we have applied the admittance spectroscopy technique to characterize DX centers in AlxGa1−xAs alloys doped with silicon. Our experimental results reveal existence of two related silicon alloys, named DX-I and DX-II centers, thermal activation energies 0.370 0.415 eV, respectively. These values are lower than those obtained by other authors using capacitance techniques. To explain disagreement it should be noticed that techniques can affected nonexponential behavior emission...

This letter predicts a strong nonlinear current density versus voltage (J-V) dependence in InAlAs/InGaAs/InAlAs double barrier resonant tunneling diodes (DBRTDs) with strained well, grown on [111] InP. The piezoelectric field generates accumulation and depletion regions both contact layers at zero bias, producing high asymmetric J-V characteristic while keeping low device series resistance. Very cutoff frequency devices, suitable for low-level microwave mixing applications, are then proposed.

We have studied a series of (111) oriented GaAs–InGaAs single quantum well, broad area lasers with active regions containing range indium concentrations, x, in order to understand the advantages and limitations pseudomorphic strain. For x⩽0.3, both an increased emission wavelength reduced threshold current were observed increasing x. The predominant cause increase is reduction bulk InGaAs band gap. attributed mainly in-plane density states caused by strain induced lifting heavy light hole...

The small gate length of high-frequency field-effect transistors (FETs) leads to situations where the role played by parasitic access regions in their circuit properties becomes dominant. Due surface band-bending effects present wide bandgap semiconductors such as GaAs or GaN, two FETs having ungated surfaces floating gates appear series with targeted one. They have be considered properly under any electrical optical stimulation applied. From point view, drain current set-up process itself...

In this work we used the differential photocurrent technique to measure strain-induced piezoelectric field in pseudomorphic InxGa1−xAs/GaAs heterostructures grown by molecular beam epitaxy on (111)B GaAs substrates. Single and multiple quantum well p–i–n diodes with two different fractions were analyzed temperature range of 25–300 K. Our results for a sample 17% fraction confirm previously reported value pyroelectric coefficient similar obtained photoreflectance spectroscopy, hence,...

By a Quantum-compliant model for electrical noise based on Fluctuations and Dissipations of energy in Complex Admittance, we will explain the phase oscillators that use feedback around L-C resonators. Under this new departs markedly from current one dissipation Thermal Equilibrium (TE), comes random series discrete previous energy, each linked with charge electron Capacitance resonator. When resonator out TE has voltage between terminals, Conversion into heat accompanies Fluctuation to...

In this work high gain GaN photoconductive UV detectors have been fabricated and characterized, a novel mechanism, dominant in these detectors, is described. DC responsivities higher than 10 3 A/W measured for an incident power of lW/m 2 at room temperature. The depends directly on the bias voltage scales with as P −k ( k ≈ 0.9) more five decades. A decrease both parameter temperature has also observed. As consequence slow non-exponential transient response, AC measurements result lower...