Low Junction Capacitance Research Articles

Photodetection properties of semiconductor laser diode detectors

Several commercial GaAlAs and InGaAsP injection lasers have been investigated with respect to their photodetection properties. The responsivity of the laser diode detectors is in the 0.15-0.25 A/W range and the dark current ranges from 5 nA to 500 nA at 3-V reverse bias. The high frequency performance of a laser diode detector strongly depends on the laser structure. The bandwidth is determined by the capacitance of the lasers and ranges from 70 MHz to 1.3 GHz. The structure showing the fastest response was the TJS laser due to its low junction capacitance.

High-temperature aging tests on planar structure InGaAs/InP PIN photodiodes with Ti/Pt and Ti/Au contact

Planar structure InGaAs/InP PIN photodiodes having low dark current and low junction capacitance characteristics were reproducibly fabricated by using VPE wafers. Bias/temperature life testings for the diodes showed that there were no significant degradations after 5500 h aging at 250°C and 10 V reverse bias by adopting the Ti/Pt and Ti/Au metals for the p-side contact.

A novel self-aligned isolation process for VLSI

We have developed a novel NMOS process for VLSI isolation. The process employs an RIE of the field oxide followed by a metal liftoff and a high-energy boron sheet implant. The energy of the implant and the metal thickness are selected such that the boron penetrates the field oxide, but not the metal. Performing the isolation doping after growing the field oxide eliminates encroachment of the isolation doping into the channel end while simultaneously providing a self-aligned channel stop. The doping concentration in the channel region is determined by implants that are independent of the doping concentration in the channel stop area. With this technique, we have obtained excellent device performance as well as rigorous device isolation. Even at the isolation spacing of 0.7 µm, there was <1-pA leakage at 5 V. The active devices exhibit minimal body effect coefficients (0.1-0.2), good subthreshold behavior (80 mV/DEC), and low junction capacitance. The experimental data is confirmed by two-dimensional analysis.

Characterization of In0.53Ga0.47As photodiodes exhibiting low dark current and low junction capacitance

The preparation and properties of grown p-n homojunction In <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</inf> Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</inf> As photodiodes for operation in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-1.7 \mu</tex> m wavelength range are described. At a reverse bias of 20 V, these diodes exhibit generation-recombination limited dark current as low as <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2 \times 10^{-9}</tex> A, junction capacitance of 0.3 pF, and pulse response corresponding to a circuit-limited rise time of 60 ps and diffusion-limited full width (FWHM) of 140 ps.

Zn Diffusion in InxGa1-xAs with ZnAs2 Source

By using ZnAs2 as a diffusion source, Zn has been diffused into InxGa1-xAs over the whole range of composition x at temperatures between 500°C and 600°C. The measured activation energy and crystal composition dependence of the diffusion coefficients and Zn surface concentration are compared with the two diffusion models so far proposed and are found to agree with the interstitial (Zni2+)-substitutional (Zns-) model. Empirical formulas describing the dependence of junction depth, hole concentration, hole mobility and diffused layer resistivity on crystal composition x, diffusion time t and temperature T are derived. Planar photodiodes, fabricated by preferential Zn diffusion in InxGa1-xAs VPE layers, exhibit microplasma-free uniform breakdown with higher breakdown voltage than 100 V, low junction capacitance of 0.24 pF for 100 µm diameter and low dark current density of 10-6 to 10-5 A/cm2.

In 0.53 Ga 0.47 As p-i-n photodiodes for long-wavelength fibre-optic systems

We describe p-i-n photodiodes fabricated from In0.53Ga0.47As grown lattice-matched on InP substrates. These diodes exhibit low junction capacitance (C&lt;1 pF at 20 V reverse bias), low dark current (≈10 nA), high break-down voltage (110 V) and wide photoresponse extending beyond 1.7 μm.

Threshold Voltage Characteristics of Double-boron-implanted Enhancement-mode MOSFETs

Threshold voltage characteristics are presented for a double boron-ion-implanted n-channel enhancement MOSFET device for high speed logic circuit applications. A 15-Ω-cm high resistivity p-type (100) substrate was used to achieve low junction capacitance and low threshold substrate sensitivity. A shallow boron implant was used to raise the threshold voltage, and a second, deeper, boron implant was used to increase the punch-through voltage between the source and the drain. This design is especially beneficial for short channel devices, while maintaining the low junction capacitance and low threshold substrate sensitivity of the high resistivity substrate. A one-dimensional analysis was performed to predict the effects of ion implantation dose and energy on the device characteristics, and a quasi two-dimensional analysis was used to account for the short channel effect. The calculated results agree well with the behavior of experimental devices fabricated in the laboratory.

Radiation and the I?V characteristic of small Josephson junctions

A calculation of the I–V characteristic and radiation spectrum of small Josephson junctions is given which takes into account the contribution to the tunneling current from the interference term and contributions to the current that are second order in the tunneling probability. The nonlinear dependence of the Josephson current on the phase difference of order parameters of superconducting films is taken into account exactly. The exact solution for the I–V characteristic of the junction is obtained in the form of an operator. Calculations are presented for the case of low junction capacitance.

"Properties and applications of diffused junction silicon rectifiers"

Developments in the diffusion technology of silicon p-n junctions have made feasible new rectifiers of outstanding performance. Current densities greater than 1,000 amperes/cm2are obtained at one volt forward bias; the same elements have reverse breakdown in excess of 200 volts. The oven diffusion method permits the critical process steps of barrier formation and contact application to be done on entire silicon slices, which may then be cut into elements of any desired size for assembly into completed devices. The use of high resistivity silicon as starting material, combined with a long diffusion cycle, results in relatively low junction capacitance. Signal type diodes have been prepared with a forward current greater than one ampere at one volt, reverse current less than one microampere at two hundred volts, and capacitance less than ten micromicrofarads at ten volts reverse bias.