Planar Doped Barrier Diodes Research Articles

On the origin of the turn-on voltage drop of GaN-based current aperture vertical electron transistors

Non-linear output characteristics and the related turn-on voltages of GaN-based current aperture vertical electron transistors (CAVETs) are investigated experimentally. The resistive components are systematically analyzed in dependence of the device layout to determine the dominant resistances in the devices. Current–voltage (IV) and capacitance–voltage-characteristics (CV) are compared to a proposed planar-doped barrier diode (PDBD) model, and the influence of the bound sheet charge density and drift layer carrier concentration is discussed. The observed CV characteristics are in contrast to the PDBD model as a clearly voltage-dependent capacitance was observed and dopant-diffusion forming a p-type aperture was ruled out. Thermionic emission was verified by temperature-dependent IV characteristics indicating interface states causing a potential barrier. Transient drain current measurements revealed a single dominating trap level with an activation energy of EA = 1.086 ± 0.015 eV. This activation energy was attributed to carbon-related acceptor states present at the regrowth interface and the drift layer. Additional test structures revealed that the interface potential barrier and the space charge in the drift layer limit the initial charge transport causing a turn-on voltage in the devices. The results point out the significance of a precise control of the regrowth interface properties and the effective carrier density in the drift layer to enable efficient, high-power devices based on the CAVET technology.

Investigating effect of temperature on barrier height of PWB diodes

The effect of temperature on the barrier height of a gallium arsenide (GaAs)/aluminium GaAs (AlGaAs) potential-well barrier (PWB) diodes is investigated and reported in this Letter. It was found that more electrons diffuse from the doped AlGaAs(silicon) into the undoped layers with increasing temperature, this modifies the electric field along these layers and hence the barrier height. The barrier height increases with increasing temperature at an increasing rate of 0.093 – 0.36 meV / K in the temperature range of 200–380 K in a similar way to the planar-doped barrier (PDB) diode. The result of the computer simulations, however, shows that the PWB diode is less sensitive than the PDB diode due to the active nature of the charge in the well.

A Hybrid Planar-Doped Potential-Well Barrier Diode for Detector Applications

This paper presents the principle of design and experimental demonstration of a prototype novel planar-doped potential-well barrier (PWB) diode concept that exploits the characteristics of both the PWB and planar-doped barrier (PDB) diodes. The highly doped (Be) sheet charge and potential well are inserted asymmetrically at nearly the same position within an intrinsic region to form a barrier. The hybrid device is designed so that the $\delta $ -doping is used to achieve a desirable minimum barrier height, while the active nature of charge in the potential well is used to enhance the device reverse bias performance. The diode achieved an ideality factor of 1.36 and corresponding voltage responsivity of 10900 V/W at 10 GHz. Diodes of this kind demonstrates promising RF signal detection and can be used in heterodyne applications. An estimated curvature coefficient of 21.2 $\text{V}^{-1}$ at a bias of 0.72 V and cut-off frequency of 47.4 GHz were realized. Results of simulation and experiment have shown excellent agreement and an improved asymmetric behavior in the ${I}$ – ${V}$ characteristics in comparison to an equivalent PDB diode.

GaAs/AlGaAs potential well barrier diodes: Novel diode for detector and mixer applications

Heterostructure potential well barrier (PWB) diodes in GaAs/AlGaAs system operating in a similar way to Planar Doped Barrier (PDB) diodes, though exploiting a potential well to trap charge, rather than a fixed doping spike have recently been realized and reported in the literature. This paper analyses the complex operation of these devices and determines the sensitivity of the current–voltage (I–V) characteristics to various design parameters. The PWB diode displays a significant temperature sensitivity, opposite in nature to PDB temperature dependence, and this suggests the possibility of temperature stabilised hybrid designs. The active bias dependence nature of charge within the well is found to have a significant effect on the device and impacts the ideality factor, which is more bias dependent than other comparable devices such as PDBs. However, the same mechanism offers the prospect of improvement in the current asymmetry and this effect can be greatly improved upon by changing the design and shape of the potential well.

Potential Well Barrier Diodes for Submillimeter Wave and High-Frequency Applications

A GaAs-based potential well barrier (PWB) diode having a $n^{++}-i-n^{++}$ epitaxial structure has been successfully designed and demonstrated. The diode uses a GaAs potential well inserted between two intrinsic AlGaAs regions in which charges accumulate to form a barrier. The device is similar in operation to a planar doped barrier diode. Results of simulations have shown good agreement with an experiment and a promising asymmetric behavior in the I–V characteristics as well as a low turn-ON voltage capability. The asymmetric structures of the PWB diode can be controlled by varying the lengths of intrinsic regions and the size and depth of the well. Simulation results using drift-diffusion and Monte Carlo models demonstrate that charge in the well is a function of bias in such a way as a higher barrier exists in reverse bias than in forward. The active nature of this variation offers potential improvements over PDB structures where the charge is defined by doping. The diode demonstrates promising RF signal detection capability with a voltage responsivity of 6.4 mV/ $\mu \text{W}$ at 10 GHz. Such a potential well-tailored diode can find exciting applications in zero bias detectors.

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.

DC and RF characteristics of MBE grown GaAs barrier diode

Schottky barriers are used extensively in high frequency switching, mixing and rectifying circuit for their good DC and RF characteristics. In this paper we report that devices measured in a double-balance mixer circuit show that the typical value of the DBS noise figure of the mixer diode is 6.1 dB at 89.5 GHz. Very good results were also observed in the 12.5, 8, 5 and 4 mm bands. However, the barrier height is virtually constant and the operation stability depends strongly on the metallurgy of the Schottky contact. In addition, properties of planar doped barrier (PDB) diodes with an n +/i/p +/i/n + configuration grown by molecular beam epitaxy (MBE) with precise control of the barrier height, were also studied. The results of artificial tailored I– V characteristics, junction capacitance and the detector application are also presented.

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.

MBE Grown Planar Doped Barrier Diodes

The realization of Planar Doped Barrier Diode (PDBD) presented in this paper starts out from the limits of the MBE layer growth technology. The limitations due to the background doping concentration and the diffusion of the n and p type dopants during the epitaxial growth are considered. The next parameter is the height of the potential barrier. The choice of this value depends on the requirements of the application. It must take into consideration the current transport mechanisms and the current limitation appearing at higher bias levels.

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 performance of 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.

The fabrication and performance of planar doped barrier diodes as 200 GHz subharmonically pumped mixers

The PDB (planar doped barrier) diode consists of a p/sup +/ doping spike between two intrinsic layers and n/sup +/ ohmic contacts. Such devices can have an anti-symmetric current vs. voltage characteristic. The capacitance is approximately constant with the applied voltage, and the barrier height and device capacitance are easily adjustable. These characteristics make the PDB a candidate for millimeter- and submillimeter-wave subharmonic mixers. We have fabricated 2 and 4 /spl mu/m diameter diodes with different barrier designs using GaAs epi-layers. The devices are planarized using an air-bridge and a surface channel etch. After completely removing the substrate, the devices are mounted on a quartz substrate to reduce parasitic effects. Diced diodes were tested as subharmonic mixers around 200 GHz in both a quasi-optical planar wideband subharmonic receiver and a planar-diode waveguide-mixer. The quasi-optical measurements show that a 0.23 V (and 0.4 V) barrier height GaAs diode with 2.0 /spl mu/A (and 5 nA) of saturation current gives a DSB conversion loss of 10.8 dB (and 9.5 dB) and a DSB noise temperature of 3795/spl deg/ K and 2450/spl deg/ K). The waveguide mixer measurements were made with a similar 0.23 V barrier height PDB. Such a mixer has a minimum conversion loss of 10.2 dB and noise temperature of 3570/spl deg/ K, and requires only 1.2 milliwatts of available LO power.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Study of the I–V characteristics of planar-doped-barrier electron emitters

Unlike conventional planar-doped-barrier (PDB) diodes which have relative low built-in accelerating fields, tunneling of electrons through the energy band gap becomes an important, and at times dominant, current transport mechanism under the high accelerating field which is essential for high performance PDB electron emitters. Thermionic emission across the triangular barrier is also found to be important. A systematic study on the temperature dependent I–V characteristics of PDB diodes with high accelerating field has been carried out, and different carrier transport mechanisms across the PDB diodes will be discussed in this article.