A Schottky-barrier diode with self-aligned floating guard ring

A Schottky-barrier diode with self-aligned floating guard ring is described. The device structure requires no additional mask or process step in an advanced bipolar LSI technology featuring polysilicon base contact and self-aligned emitter region [1]. In contrast to conventional guard ring structures, the guard ring is separated from the anode by a sidewall oxide of thickness less than 0.3 µm, allowing independent access to the guard ring. Near-idealI-Vcharacteristics are obtained. It is shown that the guard ring can be left floating without degrading theI-Vcharacteristics of the Schottky diode. In this mode of operation, the advantage of the guard ring is maintained while the depletion capacitance and charge storage due to minority-carrier injection from the p⁺-n junction which reduce the effectiveness of the Schottky diode as an antisaturation device are eliminated.     

Temperature variable noise and electrical characteristics ofAu-Ga-As Schottky barrier millimeter-wave mixer diodes

The fabrication and characterization of gold-gallium arsenide Schottky-barrier diodes on molecular-beam-epitaxy (MBE)-grown epitaxial gallium arsenide intended for cryogenic millimeter-wave mixer applications is reported. The Schottky barriers were formed either by pulse plating or by in situ evaporation in the MBE system after the epitaxial growth. The equivalent temperature as derived from the current-voltage characteristic is considerably lower at high current densities and cryogenic temperature than for the more commonly used Pt-GaAs Schottky diode. Noise-generation mechanisms are investigated as a function of forward bias and temperature. At cryogenic temperature, a best equivalent noise temperature of 22 K was obtained at 4 GHz for a DC-biased diode     

The fabrication of very narrow self-aligned guard rings around Schottky-barrier diodes

A new method for the fabrication of very narrow self-aligned guard rings around Schottky-barrier diodes is presented. Schottky diodes having the self-aligned guard ring show significant improvements in their reverse characteristics.     

Submillimeter-Wave Detection with Submicron-Size Schottky-Barrier Diodes

Schottky-barrier diode detection has been extended to 7.2 THz (42 mu m) using 0.5-mu m-diam diodes. The diodes were fabricated on bulk-doped n-type GaAs using electron lithographic techniques; diameters as small as 1000 /spl Aring/ have been achieved. A new approach in Schottky-barrier design, the contact array diode, is proposed. The diode is fabricated from readily available bulk doped material, and a performance is indicated that is competitive to the conventional epitaxial Schottky-barrier mixer well into the submillimeter wavelength region. A scanning electron microscope (SEM) photograph of diode array structures is shown.     

4500V碳化硅肖特基二极管研究

设计了一种阻断电压4 500V的碳化硅(SiC)结势垒肖特基(JBS)二极管。采用有限元仿真的方法对器件的外延掺杂浓度和厚度以及终端保护效率进行了优化。器件采用50μm厚、掺杂浓度为1.2×1015cm-3的N型低掺杂区。终端保护结构采用保护环结构。正向电压4V下导通电流密度为80A/cm2。     

Numerical analysis of GaAs epitaxial-layer Schottky diodes

A computer simulation of GaAs epitaxial-layer Schottky-barrier diodes has been carried out. The present work extends previous drift-diffusion equation (DDE) Schottky-barrier diode simulations to very thin epilayers of GaAs as well as to higher forward bias voltages. Diodes having epitaxial layers of 0.12 and 1.0 µm were modeled with an emphasis on comparison with experiment. To achieve better agreement with experimental data an interfacial layer was included in the model, resulting in a voltage-dependent barrier height. The bias voltage at which the I-V characteristic becomes strongly nonideal is predicted to depend more on the potential drop across the interfacial layer than on the series resistances present in the devices studied. The separate contributions of the dynamic resistance of the junction and of the series resistances of the epitaxial and bulk regions to the total resistance were examined for forward biases up to 1.1 V.     

RF Sputtered gold-amorphous silicon Schottky-barrier diodes

Gold Schottky-barrier diodes formed on reactively sputtered amorphous silicon thin films have been investigated. Device forwardI-Vcharacteristics are well modeled as a Schottky diode in series with a temperature activated series resistor. At 300K, the forward current indicates a diode correction factor of 1.4 and a saturation current of 5.8 × 10^-10A/cm². The metal-semiconductor barrier height is 0.93 eV. Capacitance versus frequency measurements indicate a depletion region thickness of 3000 Å. In the depletion region, the mobility-lifetime products are estimated to be of the order of 5 × 10^-11cm²/V which is substantially less than the value of 10^-7cm²/V in the quasi-neutral region, It is suggested that deep gap states are responsible for this difference. Carrier recombination in the depletion region limits the photovoltaic performance.     

Voltage measurement in GaAs Schottky barriers using optical phasemodulation

What are thought to be the first measurements of applied voltage in a GaAs Schottky-barrier diode using optical phase modulation are presented. A theoretical model, based on the refractive-index perturbation in a Schottky-barrier depletion region, describing these measurements was derived and gives good agreement with the observe results. The large signal response and large frequency response of the measurement system are illustrated. This technique facilitates high-sensitivity measurements of voltages in integrated Schottky diodes     

Electrical characteristics of high performance Au/n-GaN schottky diodes

Au/n-GaN Schottky diodes with the Au electrode deposited at low temperature (LT=77K) have been studied. In comparison, the same chip of GaN epitaxial layer was also used for room temperature Schottky diodes. The low temperature Schottky diodes exhibit excellent performance. Leakage current density as low as 2.55×10⁻¹¹ A·cm⁻² at −2.5 V was obtained in the LT Schottky diodes. The linear region in the current-voltage curve at forward bias extends more than eight orders in current magnitude. Current-voltage-temperature measurements were carried out to study the characteristics of the LT Schottky diodes. A typical barrier height of about 1.32 eV for the LT diode, which is the highest value ever reported, was obtained. The obvious enhancement in electrical performance makes the LT processing a very promising technique for GaN device application although the detailed mechanisms for the LT Au/n-GaN Schottky diodes are still under investigation.     

An analysis of positive and negative resistance characteristics inthe high-current-density region of Schottky diodes

A number of different diode characteristics are observed in small-area silicon Schottky diodes under forward-biased and high-current-density conditions. These characteristics, such as positive resistance, negative resistance, and normal diode characteristics, are analyzed. The analysis demonstrates that the variations are due to the minority-carrier accumulation in the epitaxial region of the diodes, which is mainly controlled by Schottky barrier heights and the resistivity of the semiconductor epitaxial region     

Schottky-Barrier Diodes for Submillimeter Heterodyne Detection

The fabrication and packaging techniques which were used to produce high-reliability mixer diodes for millimeter-wave satellite communications systems have been extended to produce Schottky-barrier mixer diodes for use in the submillimeter-wave region from 1 to 0.1 mm. The influence of material and circuit parameters on the performance of Schottky-barrier diodes as heterodyne detectors in the submillimeter-wave region has been considered. The semiconductor material parameters have been optimized and new packaging concepts have been investigated. A new diode package has been developed which incorporates both an integral stripline filter on 0.05-mm-thick quartz and a section of overmoded waveguide. The new package has the advantage of being replaceable in the mixer circuits, and yet it can provide a low-loss interface between the diode package and the mixer circuit. A new surface-oriented device has been developed in which the contact to the Schottky barrier is formed by photolithographic techniques onto the same surface as the ohmic contact. The surface-oriented devices exhibited heterodyne detection into the submillimeter region.     

Performance of W-InSb Metal-Semiconductor Point-Contact Diodes as Detectors and Mixers in the Near Infrared

Metal-Insulator-Metal (MIM) and Schottky-barrier diodes have been used extensively in the past years as harmonic generators and mixers for frequency measurements in the spectral range from the far-infrared to the visible. MIM diodes present a very low fabrication cost and are easy to handle, while Schottky diodes are mechanically more stable and long-lived. In the present work we discuss the performance of a metal-semiconductor point-contact diode for the radiation around 1 μm. This device, which may be viewed as a hybrid between a MIM and a Schottky diode, combines the simplicity and easiness of fabrication of the MIM diode with the stability and the long contact life typical of the Schottky diode. It proved to be very efficient even for visible light.     

Edge leakage control in platinum-silicide Schottky-barrier diodesused for infrared detection

Platinum silicide (PtSi) on p-silicon Schottky-barrier focal plane arrays (FPAs) are strong candidates for infrared (IR) detection up to a wavelength of about 5 μm. However, an inherently low quantum efficiency (about 1% at 4 μm) makes it important to maximize the fill factor or the area of the array that is IR-sensitive. Current designs use an n^- guard ring around the PtSi diodes to suppress edge leakage. This is effective, but the guard-ring overlap can significantly reduce the sensitive area of the diode. An aluminium plate that is already used as a photon reflector above the diode in current designs can be positively biased as a field plate to create a surface depletion layer around the diode periphery. This produces leakage current suppression equivalent to the guard ring without giving up IR-sensitive diode area     

A 2-dimensional fully analytical model for design of high voltage junction barrier Schottky (JBS) diodes

A physics-based closed form analytical model for the reverse leakage current of a high voltage junction barrier Schottky (JBS) diode is developed and shown to agree with experimental results. Maximum electric field “seen” by the Schottky contact is calculated from first principles by a 2-dimensional method as a function of JBS diode design parameters and confirmed by numerical simulations. Considering thermionic emission under image force barrier lowering and quantum mechanical tunneling, electric field at the Schottky contact is then related to reverse current. In combination with previously reported forward current and resistance models, this gives a complete I-V relationship for the JBS diode. A layout of interdigitated stripes of P-N and Schottky contacts at the anode is compared theoretically with a honeycomb layout and the 2-D model is extended to the 3-D honeycomb structure. Although simulation and experimental results from 4H-Silicon Carbide (SiC) diodes are used to validate it, the model itself is applicable to all JBS diodes.     

平面肖特基二极管的制作

为研究制作THz频段下工作的肖特基二极管器件,系统研究了平面肖特基二极管的制作工艺。通过分子束外延(MBE)生长了掺杂浓度分别为5×1018 cm-3的缓冲层和2×1017 cm-3的外延层,并研究温度对厚度的影响,使得膜层厚度控制良好,晶格完整。通过参数控制,减小了等离子体增强化学气相沉积(PECVD)的SiO2钝化层应力,使压指结构的翘曲情况得以改善。研究了不同退火温度下欧姆接触的情况,使接触电阻率减小到0.8×10-7 ?/cm2。用电子束光刻和干法刻蚀制作了亚微米级的阳极区域,结合GaAs湿法刻蚀的速率控制,完成了表面沟道的制作,制作出完整的平面肖特基二极管。通过I-U曲线理论计算,二极管的截止频率达到太赫兹量级,为后续工作奠定了基础。     

Edge injection currents and their effects on 1/f noise in planar Schottky diodes

A technique has been devised whereby the foreward bias edge current of a planar Schottky diode can be separated from the area current. The saturation current density and ideality factor of this edge current have been measured, the edge saturation current density being related to the area saturation current density by a newly defined edge figure of merit, M_e. The area current agrees very closely with the thermionic emission Schottky diode equation, whereas the edge currents exhibit serious departures from this equation. No guard rings or process steps other than those normally used to fabricate diodes are needed to obtain these measurements. An ultra-low-noise preamplifier has been constructed which is sufficiently sensitive to detect the difference between the thermal noise of a short and a 5 ohm resistor. Noise power levels approaching $\text{case1}\text{2}\text{kT}$ (pure shot noise) have been observed in unpassivated Schottky diodes. The low frequency noises (1/f noise) of planar Schottky diodes has been measured and correlated with the edge currents, the correlation being expressed in the form of a newly defined noise figure of merit, M_n. The technique and figures of merit are universally applicable to all forms of planar diode structures, including Schottky barrier and diffused junction types.     

The Mott diode as a heterodyne receiver element

This paper considers a novel doping profile for Schottky barrier mixer diodes called the Mott barrier. The structure consists of a metal-semiconductor junction in which the semiconductor's epitaxial layer is very lightly doped and thin enough so that it remains depleted even under substantial forward bias. It has been proposed that Mott barrier diodes will generate less noise and have lower series resistance-junction capacitance products than standard Schottky diodes, thus increasing the sensitivity and cut-off frequency of heterodyne receivers. In this paper, the band structure and electron transport properties of the Mott diode are evaluated. This analysis shows that the Mott diode actually will have a large series resistance-junction capacitance product and excessive hot electron noise, making it a poor candidate for high-frequency applications. Experimental results are presented which substantiate these conclusions.     

Millimeter-wave diode-grid phase shifters

Monolithic diode grids have been fabricated on 2-cm square gallium-arsenide wafers with 1600 Schottky-barrier varactor diodes. Shorted diodes are detected with a liquid-crystal technique, and the bad diodes are removed with an ultrasonic probe. A small-aperture reflectometer that uses wavefront division interference was developed to measure the reflection coefficient of the grids. A Phase shift of 70° with a 7-dB loss was obtained at 93 GHz when the bias on the diode grid was changed from -3 V to 1 V. A simple transmission-line grid model, together with the measured low-frequency parameters for the diodes, was shown to predict the measured performance over the entire capacitive bias range of the diodes, as well as over the complete reactive tuning range provided by a reflector behind the grid, and over a wide range of frequencies form 33 GHz to 141 GHz. This shows that the transmission-line model and the measured low-frequency diode parameters can be used to design an electronic beam-steering array and to predict its performance. An electronic beam-steering array made of a pair of grids using state-of-the-art diodes with 5-Ω series resistances would have a loss of 1.4 dB at 90 GHz     

Low-frequency excess noise in metal—Silicon Schottky barrier diodes

Theoretical models for the generation-recombination noise and trapping noise in metal-semiconductor Schottky barrier diodes are developed. Low-frequency excess noise in Schottky barrier diodes is found to be dominated by the modulation of the barrier height φB caused by fluctuation in the charge state of traps or generation-recombination centers. This noise mechanism does not occur in p-n junctions. The bias and the temperature dependence of the generation-recombination noise is critically compared with the experimental data for forward diode current ranges from 3 to 300 µA and operating temperatures from -25° to 100°C. Trapping noise in Schottky barrier diodes is observed at low temperatures in diodes not intentionally doped with deep level impurities. The experimental results on trapping noise can be described by assuming that the trap states have a constant capture cross section and are uniformly distributed in space, as well as in energy. The surface potential at the diode periphery also has an important effect on the Schottky barrier diode noise. The best low-frequency noise behavior is found when the surface is at the flat-band condition. An accumulated surface is always associated with a large amount of low-frequency excess noise.