GaAs Planar Doped Barrier Research Articles

GaN Heterostructure Barrier Diodes Exploiting Polarization-Induced <inline-formula> <tex-math notation="TeX">$\delta$ </tex-math></inline-formula>-Doping

A GaN-based heterostructure barrier diode (HBD) similar to GaAs planar-doped barrier diodes is demonstrated. Instead of doping with impurities, the polarization-induced sheet charge at the III-nitride heterojunction behaves as an effective δ -doping. An AlGaN/GaN heterostructure is used for the demonstration. The rectifying characteristics of the polarization-induced GaN HBDs can be tuned by controlling the graded AlGaN thickness and composition. Such polarization-engineered HBDs can find applications in high-voltage and high-frequency electronics.

Optimization and Realization of Planar Isolated GaAs Zero-Biased Planar Doped Barrier Diodes for Microwave/Millimeter-Wave Power Detectors/Sensors

A high tangential signal sensitivity (TSS) zero-bias GaAs planar doped barrier (PDB) diode for microwave and millimeter-wave power detection applications is presented. The fabricated PDB diodes have shown 4 dB better TSS at 35 GHz than that of reported devices, considerably increasing the minimum detectable power and widening the dynamic range. The high TSS was obtained by optimizing the PDB layer structures, namely, the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$delta$</tex> -doped <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$hboxp^++$</tex> layer and the two intrinsic layers, and by employing ion bombardment to better define the device and reduce parasitic effects. The isolation properties of ion bombarded epitaxial layers on GaAs substrates were examined and optimized to have a sheet resistivity of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$hbox10^8~Omega/hboxsq$</tex> . The temperature dependence of the barrier height of the PDB diode has been investigated experimentally, showing positive temperature coefficient and, hence, better thermal stability. We have also defined the critical barrier height and derived its analytical expression, which gives the theoretically lowest possible barrier height of a PDB diode.

High tangential signal sensitivity GaAs planar doped barrier diodes for microwave/millimeter-wave power detector applications

Tangential signal sensitivity (TSS) of GaAs planar doped barrier (PDB) detector diodes as low as -55 dBm at 35 GHz has been achieved. In comparison with that of reported devices, this value is 6-dBm better, implying the diodes can detect much lower power hence widening the dynamic range of microwave/millimeter-wave power detectors.

Electrical isolation, thermal stability and rf loss in a multilayer GaAs planar doped barrier diode structure bombarded by H+ and Fe+ ions

Electrical isolation in multilayer GaAs planar doped barrier (PDB) diode structures produced by H+ and Fe+ ion implantation were investigated. For an H+ bombardment with a dose of 1×1015 cm−2, a sheet resistivity as high as 3×108 Ω/sq and thermal stability up to 400 °C has been achieved. For samples bombarded by Fe+ ions, a similar high sheet resistivity has also been achieved although a longer annealing time (15 min) and a higher annealing temperature (550 °C) were needed. The rf dissipation losses of coplanar waveguide (CPW) “thru” lines fabricated on bombarded multilayer PDBD structure samples were also examined. The measured rf losses were 1.65 dB/cm at 10 GHz and 3 dB/cm at 40 GHz, similar to the values that a CPW line exhibits on a semi-isolating GaAs substrate.

High voltage sensitivity GaAs planar doped barrier diodes for microwave/millimetre-wave zero-bias power detector applications

GaAs planar doped barrier zero-bias detector diodes with voltage sensitivities of as high as 17 mV/µW at 10 GHz and 29 mV/µW at 35 GHz have been successfully designed, fabricated and tested. In comparison with existing devices, these sensitivities are 3–10 times higher, implying that the diodes can detect much lower RF power.

Experimental verification of barrier height temperature dependence in GaAs planar doped barrier diodes

The effect of temperature variation on barrier height of a GaAs planar doped barrier (PDB) diode has been investigated. Measurements show that the barrier height of such a device increases with increasing temperature, by the rate of 0.25 to 0.3 meV/K for the temperature range 200–360 K. Although it has been theoretically predicted (by Kearney, Dale and colleagues) that the PDB diode has a positive temperature coefficient, this is understood to be the first time that such prediction has been verified experimentally.

GaAs planar doped barrier diodes

The planar doped barrier diodes are majority carrier devices with technologically controlled barrier height. This paper reviews the main current conducting mechanisms. The limits of the I–V characteristics are described. The design of the device is shown on an example. The measured and calculated characteristics agree well.

Impact ionisation in GaAs planar-doped barrier structures grown by molecular layer epitaxy

The I–V characteristics and substrate current of GaAs planar-doped barrier (PDB) n+-i-p+-i-n+ structures with various barrier heights (0.5–0.8 V) grown by molecular layer epitaxy (MLE) have been measured at temperatures ranging from 77 to 296 K. The measurement was carried out at the constant source–drain distance of 1000 Å. It is found that an abrupt increase in the drain current occurs, in the high barrier (&gt;0.73 V) PDB structures at a threshold bias voltage VTH. The value of VTH decreases from 3.1 to 2.7 V with increasing temperature from 77 to 296 K, and the coefficient is –1.8 mV/K. The ratio of VTH and GaAs bandgap Eg is obtained to be eVTH/Eg ≈ 2. The mechanism of the abrupt increase in the drain current is attributed to the effects of ballistic electron transport and the lowering of the potential barrier by the accumulation of impact-ionisation-generated holes at the p+ plane. Furthermore, this mechanism is confirmed by the results of photocurrent measurements, in which holes are generated by incident light. The obtained results have important implications for the design of the barrier height in PDB structures and other devices having thin potential barriers.

Tunnelling currents in very thin planar-doped barrier n+-i-p+-i-n+ structures

The GaAs planar doped barrier (PDB) n+-i-p+-i-n+ structures with different barrier heights and thicknesses are fabricated by the molecular layer epitaxy (MLE) method. The tunnelling probabilities of these structures are calculated, based on the triangular potential barrier model, using WKB approximation. The calculated tunnelling currents for the PDB structures with designed source–drain distances of 460 Å and 1000 Å are in good agreement with the experimental data at 40 K ~ 173 K and 40 K ~ 77 K, respectively. This indicates that the dominant transport mechanism in these structures is tunnelling in these temperature regions. The current transport in the thinner PDB structures with metallurgical source–drain distances of 110 Å is dominated by tunnelling even at room temperature, but modelling of I–V characteristics for such thin structures should account for the n+ layer&apos;s depletion.

Hot-Electron Noise in a GaAs Planar-Doped Barrier Diode: Experiment and Monte Carlo Simulation

Hot-Electron Noise in a GaAs Planar-Doped Barrier Diode: Experiment and Monte Carlo Simulation

Competition of shot noise and hot-electron noise in GaAs planar-doped barrier diode

Microwave noise in GaAs planar-doped barrier diodes is investigated over a wide range of bias. Suppression of shot noise at intermediate densities of current and an onset of hot-electron noise at high densities are evidenced by experimental data and Monte Carlo simulation.

A comparison of planar doped barrier diode performance versus Schottky diode performance in a single balanced, MIC mixer with low LO drive

This paper demonstrates that an unbiased GaAs planar doped barrier (PDB) diode, single balanced, Ku-band mixer achieves conversion loss performance comparable to a bias-optimized GaAs Schottky design at low local oscillator (LO) power levels for identical RF circuits. An experimental, side-by-side, performance comparison as a function of LO power is presented along with a harmonic balance (HB) simulation. The PDB diode is of interest for its zero-bias requirement and the high pulsed peak power handling potential for low-cost radars. >

Effect of proton isolation on DC and RF performanceof GaAs planar doped barrier diodes

Planar doped barrier (PDB) diodes have been fabricated using both mesa and proton implant isolation. Comparative measurements of DC characteristics, RF noise figure and tangential sensitivity indicate that proton implant isolation gives devices of favourable performance following annealing at 290°C for 20 min, with the advantage of a planar process.

Neutron radiation effects in GaAs planar doped barrier diodes

The degradation of GaAs planar doped barrier diodes subject to neutron irradiation is discussed. It is shown that for fluences as high as 10/sup 15/ cm/sup -2/, the diode characteristics are very well preserved, which strengthens the rationale for using these devices in place of Schottky diodes in harsh working environments such as nuclear instrumentation and space.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

GaAs planar-doped barrier vacuum microelectronic electron emitters

A novel vacuum microelectronic electron emitter has been demonstrated in GaAs by using a planar-doped-barrier (PDB) structure. Emitted electrons are collected in high vacuum by a tantalum anode placed approximately 1 mm away from the emitter surface. Surface passivation with (NH/sub 4/)/sub 2/S/sub x/ followed by in situ heating in vacuum has been used to obtain an atomically clean surface. An emission current density of 0.42 A-cm/sup -2/ and an efficiency of 0.3% have been obtained from a 60 mu m*60 mu m emission region with an anode bias of 100 V.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

GaAs planar doped barrier diodes for millimetre-wave detector applications

Epitaxially grown GaAs planar doped barrier diodes have been designed and fabricated into coplanar structures specifically for millimetre-wave zero-bias detector applications. Results at 35 GHz and 94 GHz show that the tangential sensitivity, voltage sensitivity and dynamic range of these devices can significantly exceed those of any comparable Schottky diode detector. This is the first report of such a result.

Hot-electron properties of GaAs planar-doped barrier diodes

A study has been made of hot-electron effects in various designs of GaAs planar-doped barrier diodes under high bias. Monte Carlo simulations suggest that hot-electron intervalley transfer provides a fundamental limit to the resistance of these devices. From our results, we speculate on an upper cutoff frequency of 350 GHz for planar-doped barrier diodes.

Hot electron spectroscopy

Using a modified GaAs planar doped barrier transistor, grown by MBE, we are able to determine the nonequilibrium distribution function of hot electrons arriving at the base/collector junction. Knowledge of the electron distribution allows one to determine the physical processes necessary for the understanding of hot electron transport which assumes prominence as device dimensions decrease.

Importance of electron scattering with coupled plasmon-optical phonon modes in GaAs planar-doped barrier transistors

The GaAs planar-doped barrier (PDB) transistor is an MBE-grown structure which employs two unipolar homo junction barriers. One barrier, the emitter, injects energetic electrons into a thin n-type base region where these electrons are intended to experience negligible energy relaxation and thereby surmount the second (collector) barrier. Maximum common-base current gain or α values of 0.75 have been obtained at 77 K in experimental devices with base widths of 870 Å. Microwave measurements from 2 to 18 GHz on these devices imply a unity common-emitter current gain frequency f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> of ∼ 40 GHz. The observed α values in other devices are unfortunately lower than those predicted by recent Monte Carlo simulations, and an unexpectedly strong dependence of α on ambient electron density in the base is noted. These are attributed to the previously overlooked electron scattering with coupled plasmon-optical phonon modes, and to electron-electron scattering. These scattering mechanisms must be included in any accurate model of energetic electron transport in GaAs in regions where the concentration of cooler ambient electrons is above 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">17</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> .

VA-7 GaAs planar doped barrier transistors

VA-7 GaAs planar doped barrier transistors