Generation-recombination noise produced in the channel of JFET's

Measurements are presented of noise in JFET's at low temperatures (80-200 K) for devices having a low pinch-off voltage. The noise spectra show the presence of several types of generation-recombination g-r processes. Two processes are attributed to traps in the channel. Further, at the lowest temperatures a long plateau, associated with donor transitions, is observed.     

Cryogenic noise performance of HEMTs and MESFETs between 300 and700 MHz

The authors present the noise performance of amplifiers using HEMTs and MESFETs at room temperature and cryogenic temperatures, in the frequency range 300-700 MHz. Results demonstrate that these microwave devices can be applied at frequencies down to at least 300 MHz, giving amplifier noise temperatures below 2 K at 20 K ambient temperature     

Design considerations for improving low-temperature noise performance of silicon JFET's

A study of the effects of channel doping and device geometry variations on the operation of silicon JFET's has been carried out in an attempt to optimize the noise performance of such devices at low temperatures. In order to obtain optimum performance at temperatures below 125°K, low values of channel doping and large channel dimensions must be used. The high frequency electrical performance of such devices is poor because of larger parasitic capacitances.     

Temperature-sensitive asymmetrical bipolar resistive switches of polymer:nanoparticle memory devices

The interface between two bulk electronic materials can significantly affect the electrical behavior of electronic devices. But the interface between a bulk metal and metal nanoparticles has been rarely explored. This paper reports significant temperature effect on the asymmetrical resistive switches of polymer:nanoparticle memory devices. The devices have architecture of a polystyrene layer admixed with gold nanoparticles capped with conjugated 2-naphthalenethiol sandwiched between Au and Al electrodes. The devices exhibit significant resistive switches at room temperature. However, the resistive switches become less significant at temperature below 200 K, and they are not noticeable at 103 K. The temperature effect suggests that the resistive switches are assisted by the thermal energy. The charge transport through the devices has different mechanisms at high and low temperatures. At temperature above 220 K, the Poole–Frenkel emission is an important mechanism for the charge transport. At temperature below 220 K, the temperature-independent Fowler–Nordheim tunneling becomes an important process.     

Temperature dependence of 1/f noise in Hg1-xCdxTe MIS infrared detectors

We measured 1/f noise on Hg_0.71Cd_0.29Te Metal-Insulator-Semiconductor (MIS) infrared detectors operated over the temperature range of 40 K to 90 K under 300 K Infrared (IR) radiation. The purpose of the study was to identify the sources of 1/f noise, especially in relation to the dark current. The devices were operated in the correlated double sampling mode where the voltage across the MIS capacitor was sampled at empty potential well and right after the accumulation of minority carriers in the well due to IR radiation generation. The noise power spectral density for the charge integrated in the MIS well was investigated in relation to the dominant component of dark current. At lower temperatures T⩽65 K, the charge noise power spectral density was found to depend quadratically on the dark current. At higher temperatures, this quadratic dependence did not exist. We attribute the dark current to a mixture of tunneling and depletion-region-originated minority carrier generation which seems to be responsible for 1/f fluctuations in these structures for temperatures below 65 K     

Trap studies in GaInP/GaAs and AlGaAs/GaAs HEMT's by means oflow-frequency noise and transconductance dispersion characterizations

The presence of traps in GaInP/GaAs and AlGaAs/GaAs HEMT's was investigated by means of low frequency noise and frequency dispersion measurements. Low frequency noise measurements showed two deep traps (E _a1=0.58 eV, E_a2=0.27 eV) in AlGaAs/GaAs HEMT's. One of them (E_a2) is responsible for the channel current collapse at low temperature. A deep trap (E_a1'=0.52 eV) was observed in GaInP/GaAs HEMT's only at a much higher temperature (~350 K). These devices showed a transconductance dispersion of ~16% at 300 K which reduced to only ~2% at 200 K. The dispersion characteristics of AlGaAs/GaAs HEMT's were very similar at 300 K (~12%) but degraded at 200 K (~20%). The low frequency noise and the transconductance dispersion are enhanced at certain temperatures corresponding to trap level crossing by the Fermi-level. The transition frequency of 1/f noise is estimated at 180 MHz for GaInP/GaAs HEMT's and resembles that of AlGaAs/GaAs devices     

Thermal effects in JFET and MOSFET devices at cryogenic temperatures

Various JFET and MOSFET devices have been studied at LN and LHe temperatures. Transient and steady-state heating of the devices at 4.2 K is investigated and it is found that the active part of the device typically heats to a steady-state temperature of 40-60 K. A transient and steady-state heating model of the device is constructed and the results are found to be in good agreement with the measured temperatures and heating transients. Studies of the noise at the various ambient temperatures show that different physical phenomena are responsible for the noise. Low-frequency noise in JFET's seems to be of generation-recombination type. Thermal noise is prevalent in the frequency region between 100 kHz and 1 MHz. The noise in some of the MOSFET devices increases with decreased temperature and seems to be surface state or "flicker" noise, The noise in MOSFET devices is by factor 5-100 times larger than the noise in investigated JFET devices.     

Low-temperature characterization of buried-channel NMOST

A comprehensive characterization of buried-channel NMOS transistors at low temperatures down to 30 K is reported. The mobilities of both surface (accumulation) and bulk (buried-channel) electrons were determined as a function of surface electric field and gate bias voltage, respectively, at low temperatures. Both surface electron mobility and buried-channel electron mobility increase with decreasing temperatures. However, a peak in the buried-channel electron mobility is observed around 80 K if the neutral region extends to regions of high impurity concentrations near the surface. A modified MOSCAP (Poisson solver) was used to obtain spatial distributions of carriers and to predict the C-V curves. Low-frequency noise measurements at low temperatures were carried out at gate voltages corresponding to the accumulation, depletion, and inversion modes of operation of the device. In the accumulation mode, a 1/f dependence is observed similar to surface-channel devices. In the depletion mode, a generation-recombination type of noise is observed with a peak around 150 K. In the inversion mode, noise that is related to the hole inversion layer is observed     

Noise effects in bipolar junction transistors at cryogenic temperatures: Part I

Part I of this investigation involves theoretical and experimental characterization of the noise performance of modern silicon planar bipolar junction transistors (BJT's) above the 1/f noise frequency region in a temperature range of 60-300 K and for several difference bias conditions. At temperatures below approximately 110 K, an excess noise source as measured by the equivalent noise resistance RN, referred to the input of the device, common-base configuration, is revealed. This excess source, resulting from a generation-recombination process within the base region of the device, is shown to have a linear dependence on the base current and base resistance as KIB²rb'b², and an exponential dependence on temperature.     

GaAs HEMT low-noise cryogenic amplifiers from C-band to X-band with 0.7-K/GHz noise temperature

Cryogenic low-noise two-stage amplifiers were developed for frequency bands of 3.4-4.6 GHz, 4-8 GHz, and 8-9 GHz using commercial GaAs high electron mobility transistor. The performances are in very good agreement with simulations, and at a cryogenic temperature of 12 K, input noise temperatures get as low as 0.6 K/GHz (2.8 K for the 3.4-4.6 GHz LNA and 5 K for the 4-8 GHz and 8-9 GHz LNAs). Gain ranges from 25 to 28 dB. Ultralow noise temperature, low-power consumption, high reliability, and reproducibility make these devices adequate for series production and receiver arrays in, e.g., telescopes.     

1/f noise studies in uncooled narrow gap Hg1−xCdxTe non-equilibrium diodes

We have studied the 1/f noise current in narrow gap semiconductor heterostructure diodes fabricated in mercury cadmium telluride (HgCdTe) and designed to operate in a non-equilibrium mode at room temperature. HgCdTe heterostructure diodes exhibit Auger suppression giving current-voltage characteristics with high peak-to-valley ratios (up to 35), and low extracted saturation current densities (e.g., 20 Acnr⁻² at 10 pm at 295K) but high 1/f knee frequencies (e.g., 100 MHz at 10 μm at 295K). A comparison is made with the noise levels found in room temperature non-equilibrium mode heterostructure InAlSb/InSb diodes. The devices are being used at high frequencies for CO₂ laser heterodyne detector demonstrators. For the devices to be useful in low frame-rate imaging arrays, the 1/f noise level must be sufficiently low that the signal is not swamped. Ideally, the knee frequency should be below the frame rate. The relationship between the noise current and reverse bias voltage, current density, and temperature will be examined in order to attempt to identify the principal 1/f generation mechanisms.     

MWIR and LWIR HgCdTe Infrared Detectors Operated with Reduced Cooling Requirements

In this work, we analyze Auger suppression in HgCdTe alloy-based device structures and determine the operation temperature improvements expected when Auger suppression occurs. We identified critical material (absorber dopant concentration and minority-carrier lifetime) requirements that must be satisfied for optimal performance characteristics. Calculated detectivity values of Auger-suppressed and standard double-layer planar heterostructure (DLPH) devices demonstrate consistently higher maximum background-limited temperatures over a range of cutoff wavelengths and generally higher detectivity values achieved by Auger-suppressed detectors. Furthermore, these devices can operate with comparable performance at up to 100 K higher than DLPH detectors operating at reference temperatures above 100 K. Results of these simulations demonstrate that Auger-suppressed detectors provide a significant advantage over DLPH devices for high-temperature operation and are a viable candidate for thermoelectrically cooled detectors. Experimental dark current–voltage (I–V) characteristics between 120 K and 300 K were fitted using numerical simulations. By fitting the temperature-dependent I–V experimental data, we determined that the observed negative differential resistance (NDR) is due to Auger suppression. More specifically, NDR is attributed to full suppression of Auger-1 processes and partial (~70%) suppression of Auger-7 processes. After Auger suppression, the remaining leakage current is principally limited by the Shockley–Read–Hall recombination component. Part of the leakage current is also due to a residual Auger-7 current in the absorber due to the extrinsic p-type doping level. Analysis and comparison of our theoretical and experimental device results in structures where Auger suppression was realized are also presented.     

Measuring the quantum correction at zero bias in metal-oxide-metal diode noise

According to van der Ziel's interpretation of Tucker's calculation of the noise and admittance of metal-oxide-metal (MOM) diodes, these devices, when operating at high frequencies (100 GHz) and low temperatures (2 K), show a transition from quantum thermal noise at zero bias to shot noise at ±1 mV bias. By slowly modulating the bias of the MOM diode between -1 mV and +1 mV, mixing and amplifying the noise, passing it through a quadratic detector and then LF filtering the detected MOM noise power, one can display the MOM diode noise power on a cathode ray oscillograph or strip-chart recorder as a function of bias, and thus calibrate the thermal noise at zero bias against the shot noise at higher bias.     

The role of the insulator in determining 1/f noise in Hg1-xCdxTe integrating MIS devices

The low frequency 1/f noise charge found in Hg_1-xCd_xTe integrating metal-insulator-semiconductor (MIS) devices operating at 40K and low bias above threshold is found to be independent of integration time. The signal theory of random processes is utilized to demonstrate that 1/f noise charge resulting from carrier number fluctuations due to insulator traps should not depend on integration time, while 1/f noise charge resulting from 1/f noise in any current filling the MIS well should be proportional to integration time. This distinction allows for the determination of effective insulator trap densities from low temperature 1/f noise data on simple MIS structures. The technique is applied to a number of n-channel and p-channel devices and the effective trap densities in ZnS are determined.     

Cryogenic characteristics of wide-band pseudomorphic HEMT MMIClow-noise amplifiers

Two wideband (8-18-GHz) single-stage MMIC (monolithic microwave integrated circuit) low-noise amplifiers (LNAs) using 0.2-μm T-gate InGaAs pseudomorphic HEMT (high-electron-mobility transistor) technology, designed and fabricated for room temperature operation, were evaluated and compared at cryogenic temperatures below 20 K. One is a balanced design using 3-dB Lange couplers, and the other is a feedback design using a series RLC parallel feedback network. The gain flatness over the 8-18-GHz frequency band was maintained for both amplifiers at room and cyrogenic temperatures, indicating that the topology for wideband designs is insensitive to temperature of operation. As the physical temperature decreased from 297 K to below 20 K, the balanced LNA exhibited an average gain increase of 2 dB and as much as an eightfold reduction of noise temperature to 20 K, while the feedback LNA exhibited an average gain increase of less than 1 dB and an average foufold reduction of noise temperature to 50 K. The negative feedback network of the feedback LNA resulted in less gain increase and less noise temperature reduction at cryogenic temperatures     

MWIR DLPH HgCdTe photodiode performance dependence on substrate material

Mid wavelength infrared p-on-n double layer planar heterostructure (DLPH) photodiodes have been fabricated in HgCdTe double layers grown in situ by liquid phase epitaxy (LPE), on CdZnTe and for the first time on CdTe/sapphire (PACE-1). Characterization of these devices shed light on the nature of the material limits on device performance for devices performing near theoretical limits. LPE double layers on CdZnTe and on PACE-1 substrates were grown in a horizontal slider furnace. All the photodiodes are p-on-n heterostructures with indium as the n-type dopant and arsenic the p-type dopant. Incorporation of arsenic is via implantation followed by an annealing step that was the same for all the devices fabricated. The devices are passivated with MBE CdTe. Photodiodes have been characterized as a function of temperature. R₀A_imp values obtained between 300 and 78K are comparable for the two substrates and are approximately a factor of five below theoretical values calculated from measured material parameters. The data, for the PACE-1 substrate, indicates diffusion limited performance down to 110K. Area dependence gives further indications as to the origin of diffusion currents. Comparable R₀A_imp for various diode sizes indicates a p-side origin. R₀A and optical characteristics for the photodiodes grown on lattice-matched CdZnTe substrates and lattice mismatched PACE-1 are comparable. Howover, differences were observed in the noise characteristics of the photodiodes. Noise was measured on 50 × 50 μm devices held under a 100 mV reverse bias. At 110K, noise spectrum for devices from the two substrates is in the low 10⁻¹⁵ A/Hz^1/2 range. This value reflects the Johnson noise of the room temperature 10¹⁰ Ω feedback resistor in the current amplifier that limits the minimum measurable noise. Noise at 1 Hz, −100 mV and 120K for the 4.95 μm PACE-1 devices is in the 1–2 × 10⁻¹⁴ A/Hz^1/2, a factor of 5–10 lower than previously grown typical PACE-1 n⁺-on-p layers. Noise at 120K for the 4.60 μm PACE-1 and LPE on CdZnTe was again below the measurement technique limit. Greatest distinction in the noise characteristics for the different substrates was observed at 163K. No excess low frequency noise was observed for devices fabricated on layers grown by LPE on lattice-matched CdZnTe substrates. Photodiode noise measured at 1Hz, −100 mV and 163K in the 4.60 μm PACE-1 layer is in the 1–2×10⁻¹³ A/Hz^1/2, again a factor of 5–10 lower than previously grown PACE-1 n⁺-on-p layers. More variation in noise (4×10⁻¹³−2×10⁻¹² A/Hz^1/2) was observed for devices in the 4.95 μm PACE-1 layer. DLPH devices fabricated in HgCdTe layers grown by LPE on lattice-matched CdZnTe and on lattice-mismatched PACE-1 have comparable R₀A and quantum efficiency values. The distinguishing feature is that the noise is greater for devices fabricated in the layer grown on lattice mismatched substrates, suggesting dislocations inherent in lattice mismatched material affects excess low frequency noise but not zero bias impedance.     

Discrete simulation of colored noise and stochastic processes and1/fα power law noise generation

This paper discusses techniques for generating digital sequences of noise which simulate processes with certain known properties or describing equations. Part I of the paper presents a review of stochastic processes and spectral estimation (with some new results) and a tutorial on simulating continuous noise processes with a known autospectral density or autocorrelation function. In defining these techniques for computer generating sequences, it also defines the necessary accuracy criteria. These methods are compared to some of the common techniques for noise generation and the problems, or advantages, of each are discussed. Finally, Part I presents results on simulating stochastic differential equations. A Runge-Kutta (RK) method is presented for numerically solving these equations. Part II of the paper discusses power law, or 1/f^α, noises. Such noise processes occur frequently in nature and, in many cases, with nonintegral values for α. A review of 1/f noises in devices and systems is followed by a discussion of the most common continuous 1/f noise models. The paper then presents a new digital model for power law noises. This model allows for very accurate and efficient computer generation of 1/f^α noises for any α. Many of the statistical properties of this model are discussed and compared to the previous continuous models. Lastly, a number of approximate techniques for generating power law noises are presented for rapid or real time simulation     

Precision measurement method for cryogenic amplifier noise temperatures below 5 K

We report precision measurements of the effective input noise temperature of a cryogenic (liquid-helium temperature) monolithic-microwave integrated-circuit amplifier at the amplifier reference planes within the cryostat. A method is given for characterizing and removing the effect of the transmission lines between the amplifier reference planes and the input and output connectors of the cryostat. In conjunction with careful noise measurements, this method enables us to measure amplifier noise temperatures below 5 K with an uncertainty of 0.3 K. The particular amplifier that was measured exhibits a noise temperature below 5.5 K from 1 to 11 GHz, attaining a minimum value of 2.3 K/spl plusmn/0.3 K at 7 GHz. This corresponds to a noise figure of 0.034 dB/spl plusmn/0.004 dB. The measured amplifier gain is between 33.4 dB/spl plusmn/0.3 dB and 35.8 dB/spl plusmn/0.3 dB over the 1-12-GHz range.     

Flicker noise in GaAs MESFET X-band amplifiers in the temperature range 300 K to 2 K

We report measurements of the noise temperature of small-signal, low-noise X-band GaAs MESFET amplifiers from room temperature down to 2 K, at offset frequencies of several hundred hertz from the carrier and for input carrier powers from -40 to -20dBm. We observe a dramatic increase in the level of flicker noise as these devices are cooled to liquid helium temperatures, in marked contrast to the normally observed decrease in noise temperature of an unsaturated GaAs MESFET amplifier as it is cooled.     

Transport and noise in GaAs/AlGaAs heterojunction bipolartransistors. II. Noise and gain at low frequencies

For pt.I see ibid., vol.36, no.6, p.1015-19 (June 1989). Low-frequency noise measured in high-current-gain GaAs/AlGaAs double-heterojunction transistors is shown to originate from noise processes in the base. High base resistance associated with high current gain causes Johnson noise to be dominant at high frequencies and low bias, while at low frequencies interface 1/f and generation-recombination noise exceed Johnson noise over a bandwidth that increases with base current. At high forward bias, this 1/f noise saturates, but by then can extend over megahertz bandwidths. A low-frequency decrease in devices gain and an excess base voltage noise in this saturation region is explained by punchthrough and the mechanism for high gain in these devices