Modulation of 10.6-micron laser readiation by CuCl

Electrooptic properties of cuprous chloride (CuCl) have been measured at 10.6 µ. The measured electrooptic and absorption coefficients were 3.2×10^-12m/V and 0.02 cm^-1, respectively. These results indicate that CuCl will be used as a low-loss electrooptic material at 10.6 µ as well as in the visible range.     

Voltage-controlled SAW oscillator on temperature-stable quartz substrate

The frequency of a surface acoustic wave (SAW) oscillator fabricated on the temperature-stable X 33 orientation of quartz is found to vary linearily with an applied bias voltage. The fractional frequency change per unit biasing field has a value of 9.5 × 10^-12m/V. Fractional frequency changes greater than 200 ppm have been obtained.     

Ga0.47In0.53As vertical photoconductive detectors with high gain and low bias voltage

We demonstrate for the first time a long-wavelength Ga0.47In0.53As vertical photoconductive detector with very high gain, low noise, low-bias voltages, high sensitivity, and high-coupling efficiency. The detector consists of an n+InP, a Fe-doped Ga0.47In0.53As, and an n+Ga0.47In0.53As layer grown successively on a semi-insulating InP substrate. The highly resistive active layer sandwiched between two n+layers creates a uniform electric field perpendicular to the surface, producing a dc gain of 86 at bias voltages as low as 0.5 V. The noise power at 100 MHz is about 11 dB lower than that of a coplanar interdigitated photoconductive detector prepared with undoped GaInAs grown by vapor-phase epitaxy. Preliminary measurements reveal a receiver sensitivity of -28.2 dBm at a bit-error rate of 10^-9at 420 Mbit/s and a wavelength of 1.55 µm.     

Electroptic diffraction modulation in ZnO film on sapphire

An electrooptic Bragg diffraction modulator with high diffraction efficiency which utilizes a low-loss epitaxial ZnO optical waveguide on a sapphire substrate is discussed. An interdigital electrode with a spatial period of 20 μm and an aperture of 3 mm was fabricated directly on the film surface using a photolithographic technique. For the TE₀ mode at 6328 Å, a maximum diffraction efficiency of 98% has been obtained from DC to 100 kHz with an applied voltage of about 31 V. The unclamped electrooptic coefficient r ₃₃ is estimated to be 5.8×10^-12 m/V which is much larger than the clamped value of 2.6×10^-12 m/V in the literature     

Collection efficiency of drift-field photodetectors made from low-lifetime materials

The short-circuit current of a CdTe drift-field photodetector is calculated for lifetimes from 5 × 10^-10to 10^-7s. It is shown that the optimal drift-field region thicknesses for visible and near-infrared light are between 0.4 and 5 µm. A method for producing such structure is proposed.     

Efficient electrooptic modulator in InGaAlAs/InP optical waveguides

A single heterostructure InGaAlAs/InP phase modulator utilizing the quadratic electrooptic effect (QEO) is reported for the first time. The calculated value of the QEO coefficient from the measurements is 3.7×10^-19 m²/V² at 80 meV below the band edge. In addition, the linear electrooptic effect (LEO) coefficient is estimated to be 1.2×10^-12 m/V, which is comparable to that of GaAs. The propagation loss of a single mode ridge waveguide is in the range of 1.5-1.7 dB/cm, which is better than the previously reported value in this material system. The measured single mode phase shifts are 5.5 and 2.8°/V mm for TE and TM polarizations, respectively. These values are the largest reported so far in an InGaAlAs system     

Characteristics of a 1.2-µm CMOS technology fabricated on an RF-heated zone-melting recrystallized SOI

0.7-5-µm CMOSFET's were fabricated on SOI which was recrystallized using an RF-heated zone-melting recrystallization (RFZMR) method. The leakage currents of n-channel MOSFET's having gate lengths between 5- and 0.7-µm range between 10^-14and 10^-12A/µm and show no dependence on channel length. Those of the p-channel MOSFET's were 10^-14-10^-12A/µm when the gate lengths were longer than 1.2 µm, and increased when the gate lengths were shorter than 1.0 µm. The propagation delay time of the CMOSFET inverter was 0.13 ns per stage at a supply voltage of 3.5 V.     

Photodetection using photomagnetoelectric and Dember effects in gold-doped silicon

Photodetection in the visible and near IR wavelength region using photomagneto-electric and Dember effects in gold-doped silicon has been demonstrated in this note. Response time trof 0.2 µs and noise equivalent power (NEP) of 6 × 10^-10for a photomagnetoelectric (PME) cell, and tr< 0.03 µs and NEP = 2.5 × 10^-10for a Dember cell, were obtained from the present results.     

HgCdTe/CdTe heterostructure diodes and mosaics

This paper discusses the results of a study of the properties of HgCdTe/CdTe heterostructure diodes and mosaics. In this study, p-type HgCdTe epi-layers on the order of 20 µm were grown on CdTe substrates by a liquid-phase epitaxial (LPE) technique. These layers normally had a carrier concentration of 5 × 10¹⁶/cm³and a mobility of 400 cm²/V . s at 77 K. The n⁺-p junction was formed by boron ion implantation, and standard photolithographic techniques were used for the device fabrication. The diodes with no antireflection coating had a typical quantum efficiency of 40 percent. The 1/fnoise knee was on the order of 10 Hz at zero bias. Surface leakage seemed to be the dominant component for diodes at temperatures less than 77 K. From mosaic studies, it was found that the spectral spread was less than ±0.3 µm for an area as large as 12 × 20 mm. The study indicates that LPE offers a viable technique for producing high-quality HgCdTe epi-layers on CdTe.     

Polycrystalline silicon thin-film transistors on a novel 800°C glass substrate

A new polycrystalline silicon thin-film transistor (TFT) technology using a potentially low-cost glass substrate is reported. Transistors are made using modified conventional n-channel MOS processes at temperatures of 800°C or less, with a final hydrogen implantation step. These transistors show leakage currents of 2 × 10^-11A/µm of channel width, ON-to-OFF current ratios of 1 × 10⁴at Vds= 9.0 V, and good dc stability. This combination of polycrystalline silicon transistors on potentially low-cost glass substrates offers a new option in the choice of active device technology for large-area flat-panel liquid crystal displays (LCD's).     

New technique for measurement of electron saturation velocity in GaAs MESFET's

A new technique for the measurement of the electron saturation velocity in GaAs FET's is proposed using the "end" resistance measurement. The measurements performed on 1.3-µm gate-length ion-implanted GaAs MESFET's lead to the values of the saturation velocity ranging from 1 to 1.3 × 10⁵m/s.     

Hybrid IRCCD imaging array

A hybrid IRCCD for high background application has been successfully fabricated. The device consists of fifty Hg0.7Cd0.3Te detector diodes of 50-µm × 50-µm sensitive areas and a silicon CCD maltiplexer with input circuits on 40-µm centers having bucket background subtraction and blooming protection circuits. The noise-equivalent power (NEP) of the IRCCD is 5 × 10^-14W-Hz^-1/2at background photon flux level of 4 × 10¹⁵photons . cm^-2s^-1, integration time of 2 × 10^-5s, and clock frequency of 3 × 10⁶Hz. The noise source of the detector diodes limits the IRCCD performance. The IRCCD is also evaluated with the real-time raster-scanned thermal images displayed on a CRT monitor. Two-dimensional images are generated by using a scanning mirror. A fixed-pattern noise is reduced by comparison of an object video to the reference video stored in a memory. A noise-equivalent temperature difference of the system is 0.6°C at a frame rate of 30 Hz. Instantaneous field of view is 1 mrad × 1 mrad and the field of view of the system is 12° × 5.7°.     

Leakage current characteristics of offset-gate-structure polycrystalline-Silicon MOSFET's

Leakage current characteristics of offset-gate-structure polycrystalline-silicon (poly-Si) MOSFET's are studied as a function of dopant concentration Noffin offset-gate regions. Leakage current markedly decreases from 1 × 10^-9to 2 × 10^-11A at VD= 10 V as Noffis varied from 1 × 10¹⁸to 1 × 10¹⁷cm^-3. A maximum ON/OFF current ratio of 10⁸is obtained at 1 × 10¹⁷cm^-3. Calculations based on a quasi-two-dimensional model indicate that the reduction of leakage current is attributable to a decrease of the maximum lateral electric field strength in the drain depletion region. An analysis of the leakage current characteristics in terms of carrier emission from grain-boundary traps implies that thermonic emission accompanied by thermally assisted tunneling could be the dominant mechanism in determining leakage current.     

Copper-doped germanium detectors

Background limited operation of copper-doped germanium detectors has been obtained for a background as low as 10^-11watts (5 × 10³photons/second) in the 8-12 µ region. The temperature dependence of the observed responsivity for detectors, each containing the same copper concentration but having different donor concentration does not agree with any of the usual theories involving the free hole velocity, mobility, or capture cross section.     

Performance of PV HgCdTe arrays for 1-14-µm applications

Recent developments in HgCdTe epitaxial-growth techniques and device-surface passivation resulted in major performance improvements of photovoltaic infrared detectors. By utilizing CdTe substrates, thin HgCdTe layers are grown from the liquid phase with any desired composition, thereby yielding detector material with peak sensitivity that can be adjusted for a wavelength from 1 to 14 µm. Two approaches for junction formation are reported; implanted homojunction and double-layer heterojunction. Detectivity limited by background radiation (BLIP) is reported. Theoretically predicted values ofR_{0}Aare measured for diodes designed to cover the 1-3-, 3-5-, and 8-14-µm bands. The frequency and junction-bias dependence of the dark noise current are characterized at a level of 5 × 10^-15A/Hz^1/2. It is shown that the device performance at any wavelength and temperature of interest can be described in terms of generation-recombination (G-R) and diffusion of minority-carrier current mechanisms.     

Electrooptic and piezoelectric measurements in photorefractive barium titanate and strontium barium niobate

We have measured the low-frequency ("unclamped") electrooptic and piezoelectric coefficients in undoped BaTiO3and SrxBa1-xNb2O6(x = 0.61) crystals using interferometric techniques. The contribution of the piezoelectric effect to the Pockels measurements is discussed. For an applied ac electric field in the range 0.1-200 V/cm, the electrooptic and piezoelectric effects are linear in the magnitude of the applied field and independent of its frequency in the range 10 Hz-100 kHz. The unclamped electrooptic coefficients of poled BaTiO3single crystals arer_{13} = 19.5 pm 1pm/V andr_{33} = 97 pm 7pm/V, and for strontium barium niobate arer_{13} = 47 pm 5pm/V andr_{33} = 235 pm 21pm/V, all measured at a wavelength of 514.5 nm and atT = 23degC. For the barium titanate samples the measured Pockels coefficientr_{c} equiv r_{33} - (n_{1}/n_{3})^{3} r_{13} = 79 pm 6pm/V is in good agreement with the valuer_{c} = 76 pm 7pm/V computed from the above values of r13and r33, where n1and n3are the ordinary and extraordinary indexes of refraction, respectively. The measured piezoelectric ] coefficient isd_{23} = +28.7 pm 2pm/V for barium titanate, and isd_{23} = +24.6 pm 2pm/V for strontium barium niobate. We also measured the photorefractive coupling of two optical beams in the crystals, and we show that the dependence of the coupling strength on beam polarization is in fair agreement with the measured values of the Pockels coefficients.     

Source, drain, and gate series resistances and electron saturation velocity in ion-implanted GaAs FET's

Techniques which allow us to determine the series source, drain, and gate resistances and the electron saturation velocity of ion-implanted GaAs FET's are described. These techniques are based on the "end" resistance measurements. The theory of this method is developed and used for a new interpretation of the "end" resistance measurements. The values of the series resistances determined by this technique are shown to be in an excellent agreement with those obtained by the modified Fukui method. The values of the electron saturation velocity varying from 1.0 × 10⁵m/s to 1.3 × 10⁵m/s are obtained using the end resistance method. The proposed set of measurements is simple and accurate enough to be used as a routine characterization technique for GaAs FET's.     

The use of refractory metal and electron-beam sintering to reduce contact resistance for VLSI

Low contact resistance for metal on silicon is particularly important for VLSI where contact dimensions become ≤1 µm. This paper reports on e-beam sintering of refractory metal contacts on implanted n⁺- and p⁺-silicon layers. With this technique, we have obtained contact resistivities as low as 1.5 × 10^-7Ω. cm²and 1.2 × 10^-7Ω . cm²for n⁺and p⁺contacts, respectively. These values are the lowest contact resistivities which have been achieved experimentally to date. We found no measurable metal-silicon interdiffusion when e-beam sintering was used. Electron-beam-induced MOS damage, including neutral traps, can be removed by a forming gas anneal.     

Switching and memory effects in amorphous chalcogenide thin films

The performance of threshold- and memory-switching devices is discussed. The threshold devices were prepared by vacuum deposition from the Ge-As-Te-Si system and exhibited threshold voltages over a wide range from less than 2.0 V to greater than 50 V. Lifetimes of the order of 10⁶-10⁸switching operations before failure were obtained and the operation of the threshold device with a capacitative load was demonstrated. Memory-switching devices were prepared from the Ge-As-Te system. The bistable operation is discussed and it is concluded that the bistable impedance states are due to the presence, or absence, of a crystalline filament between the electrodes. Typical pulse levels required to produce the transition between the impedance states were 2 × 10^-2A for 5 × 10^-3s and 5 × 10^-2A for 5 × 10^-6s. The devices possess fairly stable characteristics and currently have lifetimes of 10²- 10³operations before failure; this is expected to improve with device development.     

Schottky barriers and ohmic contacts on n-type InP based compound semiconductors for microwave FET's

InP, and In0.73Ga0.27As0.6P0.4, and In0.53Ga0.47As lattice matched to InP are of special importance as active FET channel materials because of the high electron velocity and/or high electron mobility they offer. Using a AuGe/Ni/Au metallization system, specific contact resistances of 5 × 10^-7Ω . cm², 8 × 10^-7Ω . cm², and 5.8 × 10^-6Ω cm²were obtained for ohmic contacts on In0.53Ga0.47As, InP, and In0.89Ga0.11As0.24P0.76, respectively. Leakage currents of 10 µA at 7-V reverse bias were observed for 1 × 200-µm gates on InP. and In0.89Ga0.11As0.24P0.76FET's having a SiO2film about 50 Å thick under the gate. A thin SiO2layer underneath the gate improved the Schottky-gate I-V characteristics, but thick oxides severely degraded the microwave performance of the FET's. These excellent ohmic contacts and Schottky barriers resulted in a maximum insertion gain of 15 dB at 8 GHz and a noise figure of 2.5 dB with 8-dB gain at 7 GHz for the InP deviees. For 1.15-eV InxGa1-xAsyP1-yFET's, the resulting gain was 9 dB at 8 GHz.