Vik J. Kapoor

Submicron nickel-oxide-gold tunnel diode detectors for rectennas

Integrated circuit technology has been successfully applied to the design and fabrication of submicron metal‐oxide‐metal (MOM) tunneling diodes for application in far infrared (FIR) rectennas. The MOM diode and a stripline antenna to enhance collection of FIR radiation were integrated on a silicon substrate using state of the art microelectronic technology and were produced simultaneously. A nickel‐oxide‐gold MOM tunnel diode was made up of a 0.8‐μm‐wide nickel layer with approximately 22 A of a nickel‐oxide tunnel barrier layer on top crossed by a 0.8‐μm‐wide gold layer resulting in a junction area of 0.64 μm2 . The antenna consisted of two 0.8‐μm‐wide and 6.6‐μm‐long parallel metal conductors, one nickel and the other gold, separated by a gap of 0.8 μm. The dc current‐voltage characteristics of the MOM diode showed that the current dependence on voltage was linear about zero bias up to a bias of about 70 mV. Beyond 70 mV, the characteristics were very nonlinear. The average breakdown field was determine...

Chemical Composition, Charge Trapping, and Memory Properties of Oxynitride Films for MNOS Devices

The effect of varying the amount of oxygen in the silicon oxynitride film of a metal/nitride/oxide/semiconductor (MNOS) device was investigated to determine correlations between the chemical nature, current conduction, charge trapping, and nonvolatile memory properties of the device. Nitrous oxide gas was used to introduce oxygen in the oxynitride film during the low‐pressure chemical vapor deposition process. The atomic percentage of oxygen increased to 21, nitrogen concentration decreased by 16%, and electron trap density decreased by 12%, with a corresponding decrease in film conductivity for an increase of the nitrous oxide gas rate from 0 to 80 sccm. The oxygen was determined to be incorporated into the film by replacing nitrogen atoms and by parallel introduction of silicon‐oxygen bonds during the deposition process. Oxygen impurities tie up the silicon dangling bonds, which may be responsible for memory traps in the film, and thus a subsequent reduction of trapped charge in the oxynitride was observed. The charge decay rate is then reduced as the trap density decreases, thus enhancing the nonvolatile memory properties of the MNOS devices. The retention and endurance device characteristics also improve considerably, by 60% and from 107 to 108 cycles, respectively. The useful memory lifetime of oxynitride MNOS devices with enhanced endurance under repeated switching was much greater than MNOS devices with oxygen‐free nitride films.

Fabrication and chemical composition of RF magnetron sputtered Tl-Ca-Ba-Cu-O high Tc superconducting thin films

High‐temperature superconducing Tl‐Ca‐Ba‐Cu‐O (TlCaBaCuO) thin films were fabricated by rf magnetron sputtering on strontium titanate (SrTiO3) substrates. Thin films of 0.5–0.7‐μm thickness were deposited by pure argon sputtering from a single composite powder target of Tl2Ca2Ba2Cu3Ox at an rf power of 250 W and a pressure of 5 mTorr. As‐deposited thin films were sintered and annealed in a thallium‐rich ambient to obtain superconductivity with a zero resistance temperature (Tc0) at 107 K. X‐ray diffraction results showed highly c‐axis oriented films with Tl2Ca2Ba2Cu3Ox (2223) and Tl2Ca1Ba2Cu2Ox (2122) phases present. Auger electron spectroscopy survey and depth profiles were performed to determine the compositional uniformity and impurity contents of the thin films. X ray photoelectron spectroscopy high‐resolution spectra were obtained at the surface, in the bulk, and near the interface with the substrate. Our XPS results support two possible mechanisms for the creation of holes in the TlCaBaCuO compound:...

Fabrication of Tl‐Ca‐Ba‐Cu‐O superconducting thin films on LaAlO3 substrates

For the first time, fabrication of high‐temperature superconducting Tl‐Ca‐Ba‐Cu‐O (TlCaBaCuO) thin films on LaAlO3 substrates is reported. TlCaBaCuO thin films were deposited by rf magnetron sputtering of a single composite powder target in a pure argon plasma. The films were sintered in an excess thallium ambient at 850 °C for 15 min followed by a 30 min oxygen annealing at 750 °C. Scanning electron microscopy and x‐ray diffraction results showed the smooth and highly c‐axis oriented nature of the thin films. The temperature dependence of resistance showed the onset of critical transition temperature (Tc) at 114 K, and zero resistance at 103 K.

Plasma‐deposited germanium nitride gate insulators for indium phosphide metal‐insulator‐semiconductor field‐effect transistors

Germanium nitride (Ge3N4) films were deposited on indium phosphide (InP) compound semiconductor substrates using plasma‐enhanced chemical vapor deposition. The depositions were performed in a capacitively coupled parallel‐plate reactor using two different processes. In the first process, germane (GeH4), nitrogen (N2), and ammonia (NH3) reactant gases were used. In the second process, germane and pure nitrogen were used as reactant gases. The films were deposited using 13.56 MHz rf excitation to a typical thickness of 800 A with a refractive index of 2.11–2.16. The breakdown field strength of the films was greater than 106 V/cm. Auger electron spectroscopy did not indicate significant chemical composition differences between the two deposition processes. In order to study the feasibility of plasma‐deposited germanium nitride as a gate insulator, metal‐insulator‐semiconductor field‐effect transistors (MISFETs) with 2‐μm channel lengths were fabricated on InP. The device transconductance and threshold voltag...

Silicon Dioxide with a Silicon Interfacial Layer as an Insulating Gate For Highly Stable Indium Phosphide Metal‐Insulator‐Semiconductor Field Effect Transistors

A novel gate insulator consisting of silicon dioxide (SiO2) with a thin silicon (Si) interfacial layer has been investigated for high-power microwave indium phosphide (InP) metal-insulator-semiconductor field effect transistors (MISFETs). The role of the silicon interfacial layer on the chemical nature of the SiO2/Si/InP interface was studied by high-resolution X-ray photoelectron spectroscopy. The results indicated that the silicon interfacial layer reacted with the native oxide at the InP surface, thus producing silicon dioxide, while reducing the native oxide which has been shown to be responsible for the instabilities in InP MISFETs. While a 1.2-V hysteresis was present in the capacitance-voltage (C-V) curve of the MIS capacitors with silicon dioxide, less than 0.1 V hysteresis was observed in the C-V curve of the capacitors with the silicon interfacial layer incorporated in the insulator. InP MISFETs fabricated with the silicon dioxide in combination with the silicon interfacial layer exhibited excellent stability with drain current drift of less than 3 percent in 10,000 sec, as compared to 15-18 percent drift in 10,000 sec for devices without the silicon interfacial layer. High-power microwave InP MISFETs with Si/SiO2 gate insulators resulted in an output power density of 1.75 W/mm gate width at 9.7 GHz, with an associated power gain of 2.5 dB and 24 percent power added efficiency.

Effects of oxygen content and oxide layer thickness on interface state densities for metal‐oxynitride‐oxide‐silicon devices

The interface state density of metal‐oxynitride‐oxide‐silicon (MNOS) devices was investigated as a function of the tunnel oxide thickness and the amount of oxygen in the oxynitride films. Nitrous oxide gas was used to introduce oxygen into the oxynitride film during the deposition process. As 17 at. % oxygen was introduced into the oxynitride film, the lowest oxide‐silicon interface state density increased from 3.0 to 3.5×1011 cm−2 eV−1 for 90‐A oxide MNOS devices, and decreased from 5.1 to 3.65×1011 cm−2 eV−1 for 20 A oxide devices. The increase in interface state density with increasing oxygen for 90‐A oxide devices may be due to an increase in the loss of hydrogen passivation at the interfacial regions as more oxygen is introduced into the film. The higher interface state density for the 20 vs 90 A oxide samples, for a given oxygen content of the oxynitride films, may be due to additional contributions from the trapping states near or at the oxide‐oxynitride interface. However, the decrease in the inte...

The Combined Effect of Hydrogen and Oxygen Impurities in the Silicon Nitride Film of MNOS Devices

The combined effect of varying the hydrogen and oxygen impurities in the silicon nitride film of metal-nitride-oxide-semiconductor (NOS) devices was studied to develop a correlation among the chemical composition, current conduction, charge trapping, and memory properties of the devices. The atomic percentage of hydrogen increased in the film as a function of decreasing deposition temperature from 850 to 650 o C. Oxygen was incorporated into the film by replacing nitrogen atoms through the use of nitrous oxide gas during the film deposition process. The addition of oxygen further reduced the hydrogen concentration in the fim

High‐voltage solar‐cell chip

Integrated circuit technology has been successfully applied to the design and fabrication of 0.5×0.5‐cm planar multijunction solar‐cell chips. Each of these solar cells consisted of six voltage‐generating unit cells monolithically connected in series and fabricated on a 75‐μm‐thick, p‐type, single crystal, silicon substrate. A contact photolithic process employing five photomask levels together with a standard microelectronics batch‐processing technique were used to construct the solar‐cell chip. The open‐circuit voltage increased rapidly with increasing illumination up to 5 AM1 suns where it began to saturate at the sum of the individual unit‐cell voltages at a maximum of 3.0 V. A short‐circuit current density per unit cell of 240 mA/cm2 was observed at 10 AM1 suns.

InGaAs microwave switch transistors for phase shifter circuits

A new InGaAs insulated-gate FET (IGFET) with 1 /spl mu/m gate length and three different gate widths has been designed, fabricated and characterized as switch devices for microwave control applications in phase shifter circuits. The devices employed a plasma deposited silicon dioxide gate insulator and had multiple air bridged source regions. The details of the DC current-voltage (I-V) characteristics and small signal S-parameter measurements up to 20 GHz are presented. The switch IGFETs had a drain saturation current density of 300 mA/mm gate width with breakdown voltages of higher than 35 V. An insertion loss of 1.0, 0.6, and 0.4 dB at 10 GHz and 1.4, 0.8, and 0.4 dB at 20 GHz have been measured for the 300, 600, and 1200 /spl mu/m gate width IGFETs, respectively. Equivalent circuit models fitted to the measured S-parameters for IGFETs yielded on-state resistances from 10.7 to 3.3 /spl Omega/, off-state resistances from 734.4 to 186.8 R and off-state capacitances from 0.084 to 0.3 pF as the gate width is increased from 300 to 1200 /spl mu/m The simulation results using IGFET models for the phase shifter circuits indicated a maximum phase error of 0.11/spl deg/, 0.26/spl deg/, and 0.479 with 0.74, 0.96, and 1.49 dB maximum insertion loss and greater than 33, 26, and 19 dB return loss for the 11.25/spl deg/, 22.5/spl deg/, and 45/spl deg/ phase bits, respectively, over the 9.5-10.5 GHz frequency band. >