Measured Noise Temperature Versus Theoretical Electron Temperature for Gas Discharge Noise Sources

In the past, measured noise temperatures T/sub n/ of a few commercially available gas discharge noise sources were indicated as agreeing with the predicted electron temperature T/sub e/ of the positive column based on the von Engel and Steenbeck relationship. Data were taken over the past 2 years on argon tubes over a pressure range of 5 to 40 mm and on neon tubes at 20 mm, with current variations from 100 to 300 mAdc. These data were compared against predicted electron temperatures. For the argon tubes at pressure-radius products greater than 20 mm/spl dot/cm there appeared to be reasonable correlation between the measured noise temperature and the predicted electron temperature although it is suggested that this correlation was fortuitous. For argon pressure-radius products less than 20 mm/spl dot/cm the measured noise temperature was as much as 15 percent lower than the predicted electron temperature. For neon tubes at 20-mm pressure, with the same variation in tube radius, and for pressure-radius products less than 24.0 mm/spl dot/cm, the measured noise temperature differed even more than for argon from the predicted electron temperature. A difference of as much as 30 percent at a pressure-radius product of 3.0 mm/spl dot/cm was observed. A qualitative explanation for argon is presented based mainly on the fact that these discharges do not have a Maxwellian distribution of electron velocities nor a velocity independent electron collision frequency. For neon the wide variation was not understood.     

The self-heated 442-nm He-Cd laser: Optimizing the power output, and the origin of beam noise

Power output and beam noise parametric results are obtained for the blue transition of the self-heated He-Cd laser in tubes of 0.10-0.16-cm bore diameter. Presentation of this data in the form of performance contour maps shows that the usual scaling laws for laser discharges are accurate for this laser (<12-percent parameter variation for a 60-percent diameter variation) and is a convenient form for use in tube design. The contour maps imply the existence of a direct connection between the output and noise of this laser. A theory is proposed that the noise in the He-Cd discharge arises from the rapid increase in ionization rate due to Penning collisions as Cd is added to the He discharge. This produces a high gain in the discharge column for the growth of striation waves (which modulate the output). The theory correctly predicts the details of the laser noise behavior, showing that both the noise and output share a common origin in the Penning effect. The dependence of Cd vapor density on tube current is found, from sidelight studies, to be more pronounced in self-heated tubes (as opposed to tubes with externally heated Cd sources). A threshold dissipation value is given for puncture of the hot glass bore by the discharge (this is a common failure mode in the He-Cd laser).     

1/f noise and specific detectivity of HgCdTe photodiodes passivatedwith ZnS-CdS films

1/f noise in HgCdTe photodiodes has been measured as a function of temperature, diode bias, and dark current. The dependence of 1/f noise on dark current was measured over a wide temperature range. At low temperatures, where surface generation and leakage current were predominant, a linear relationship between 1/f noise and dark current was observed. At higher temperatures, where diffusion current is predominant, the correlation no longer holds. The temperature dependence of 1/f noise was also determined. The temperature dependence of the 1/f noise was found to be the same as that for the surface generation and leakage currents. All the data obtained in these experiments could be fit with theoretical predictions by a simple relationship between 1/f noise and dark current. The 1/f noise in the HgCdTe photodiode varies with diode bias, temperature, and dark current only through the dependence of the surface current on these devices. The maximum specific detectivity (D*) value and the maximum signal-to noise ratio are approximately 3.51×10¹⁰ cm·Hz^1/2/W and 5096 at 50 mV reverse bias, respectively     

DC conduction and low-frequency noise characteristics ofGaAlAs/GaAs single heterojunction bipolar transistors at roomtemperature and low temperatures

The DC conduction and low-frequency noise characteristics of GaAlAs/GaAs single heterojunction bipolar transistors (HBTs) have been investigated at room temperature and at temperatures down to 5 K. The collector current dependence of the current gain was investigated at various temperatures. The low-frequency noise characteristics exhibit both 1/f and generation-recombination components. The noise characteristics are sensitive to changes in base current and insensitive to changes in collector-emitter voltage, thus suggesting that the noise source is located in the vicinity of the emitter-base heterojunction. The noise spectrum follows a simple model based on minority carrier trapping effects at the heterointerface     

Noise temperature data on low pressure argon discharges

Measured noise temperatures for argon discharges at pressures from 1 to 40 mmHg in tubes with 0.63-cm inner radius are presented. In general, the results agree with theoretical electron temperatures, but disagree with previously published data for similar pressure-radius products. It is suggested that similarity rules should be applied with caution. Large audio-frequency disturbances were found to originate in the anode region at all pressures; variations in the plasma impedance were synchronized with these disturbances.     

Electron temperature in a.c. discharge excited between insulating electrodes †

The electron temperatures in a.c. discharges of frequency 50 c/s excited between plane parallel glass electrodes in air have been measured at various pressures. The electron temperatures have been computed by employing the Johnson—Malter double-probe technique. It is seen that the electron temperature increases from 8-5 × 10^{4 °} K to 12-8 7× 10^{4 °}K as the pressure is reduced from 10 Torr to 01 Torr. The nature of the variation of the electron temperature with pressure is seen to be similar to the corresponding variation in the case of d.c. discharges, as well as that in the case of audio frequency discharges between metal electrodes. This similarity indicates that, after the stable discharge is obtained, the discharge between the insulating electrodes is similar to that in the case of conducting electrodes.     

硅低温低频低噪声双极晶体管的分析与设计

对硅双极晶体管低频噪声的本征与非本征两种分量进行了系统的理论分析，并研究了各自的温度特性，在此基础上，设计并研制出一种多晶硅发射极低温低频低噪声晶体管，其等效输入噪声电压。     

Temperature dependence of multiplication noise in silicon avalanche photodiodes

The temperature dependence of multiplication noise in silicon avalanche photodiodes with a low-high-low impurity density profile is calculated. The variation of multiplication noise by temperature change can be neglected in practical use at a constant multiplication factor, which is in agreement with experimental results.     

热释电探测器外部噪声的研究

研究了ＰＥＣ结构热释电探测器的环境温度变化噪声及机械振动噪声，介绍了两种降低外部噪声的方法，得出了比探测率、环境温度变化产生的噪声与负载电阻的关系，并进行了实验验证；并对双元探测器的一些特性进行了研究。     

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.     

Efficiency and signal/noise ratio of short linear dipoles

The performance of inductively loaded dipoles as a function of coil loading position can be expressed either in terms of their efficiency or power gain, or alternatively in terms of their signal/noise ratio for different sky temperatures. The variation of power gain and efficiency with loading position differs from the corresponding variation of signal/noise ratio, and graphs illustrating the relation between signal/noise ratio and efficiency for any short dipole are provided for different sky temperatures.     

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 properties of HTS Josephson mixers at 345 GHz and operating temperatures at 20 K

The authors report on the mixing properties of high-temperature superconductor bicrystal Josephson junctions at 345 GHz and high-operating temperatures. A variable backshort and E-plane tuner enabled the control of impedance matching between the junction and the RF environment. The local oscillator frequency and intermediate frequency were 345 and 1.4 GHz, respectively. The double-side band (DSB) mixer noise temperature and the conversion efficiency were determined using the hot/cold method. The authors observed that the noise temperature was strongly dependent on the matching conditions. The lowest noise temperatures were observed for tuner positions supporting the formation of a subharmonic step which appeared between the zeroth and first Shapiro step. At T = 20 K they obtained a lowest DSB mixer noise temperature of 1003 K and a conversion efficiency of -1.2 dB. They have investigated the dependence of the noise temperature on the operating temperature in detail. The impact of resonances on the device performance will be discussed.     

Signal/noise ratio of inductive-loaded antennas

The effect on signal/noise ratio of moving an inductive load away from the drive point of a monopole antenna is studied. The variation of this ratio with load position is determined as a function of previously derived empirical expressions for relative radiation resistance and load reactance. Small signal/noise improvements can be obtained at low sky temperatures.     

Short-Wave Infrared HgCdTe Avalanche Photodiodes

Short-wave infrared (SWIR) HgCdTe avalanche photodiodes (APDs) have been developed to address low-flux applications at low operating temperature and for laser detection at higher temperatures. Stable multiplication gains in excess of 200 have been observed in homojunction APDs with cutoff wavelengths down to 2.8???m and operating temperatures up to 300?K, associated with low excess noise F?<?1.3 and low 1/f noise. The measured dark current density at 200?K of 6.2???A/cm² is low enough to enable high-sensitivity single-element light detection and ranging (lidar) applications and time-of-flight imaging. Corresponding APD arrays have been hybridized on a readout integrated circuit (ROIC) designed for low-flux low-SNR imaging with low noise and frame rates higher than 1500?frames/s. Preliminary focal-plane array characterization has confirmed the nominal ROIC performance and showed pixel operability above 99.5% (pixels within ±50% of average gain). The bias dependence of the multiplication gain has been characterized as a function of temperature, cadmium composition, and junction geometry. A qualitative change in the bias dependence of the gain compared with mid-wave infrared (MWIR) HgCdTe has motivated the development of a modified local electric field model for the electron impaction ionization coefficient and multiplication gain. This model gives a close fit to the gain curves in both SWIR and MWIR APDs at temperatures between 80?K and 300?K, using two parameters that scale as a function of the energy gap and temperature. This property opens the path to quantitative predictive device simulations and to estimations of the junction geometry of APDs from the bias dependence of the gain.     

Growth temperature dependence of low-noise MESFET in molecular-beam epitaxy

The substrate growth temperature dependence of electrical properties for a low-noise MESFET fabricated on MBE-grown material has been demonstrated. The optimum noise figure and its associated gain were attributed to the higher epilayer quality and mobility at a growth temperature of 650°C between temperatures of 550°C and 700°C.     

Low-Noise Cooled GASFET Amplifiers

Measurements of the noise characteristics of a variety of gallium-arsenide field-effect transistors at a frequency of 5 GHz and temperatures of 300 K to 20 K are presented. For one transistor type detailed measurements of dc parameters, small-signal parameters, and all noise parameters (T/sub min/, R/sub opt/, X/sub opt/ g/sub n/) are made over this temperature range. The results are compared with the theory of Pucel, Haus and Statz modified to include the temperature variation. Several low-noise ampifiers are described including one with a noise temperature of 20 K over a 500-MHz bandwidth. A theoretical analysis of the thermal conduction at cryogenic temperatures in a typical packaged transistor is included.     

Temperature dependence of 1/f noise in polysilicon-emitter bipolar transistors

1/f noise was measured on polysilicon-emitter bipolar n-p-n and p-n-p transistors over a temperature range of 173K相似文献   

Data on the Temperature Dependence of X-Band Fluorescent Lamp Noise Sources

This paper is concerned primarily with the performance of fluorescent lamps as microwave noise sources at 9,000 mc. In particular, it deals with the temperature dependence of the excess noise ratio of an 8-watt lamp running at a lamp current of 150 ma in a 10° E-plane holder. It was found that 1) the bulb temperature is much higher than that with a lamp current of 75 ma encountered in the 90° H-plane circuit investigated previously at 4,000 mc, hence the temperature coefficient of excess noise versus waveguide temperature obtained in the 4,000 mc circuit does not apply, 2) anomalous and unreproducible inversions in the temperature coefficient at these higher bulb temperatures have been observed, 3) these anomalies can be avoided by operating the bulb at lower temperatures, 40°C to 50°C, where the lamps appear to be just as uniform and stable and probably just as noisy as they are at 4,000 mc.     

Temperature dependence performances of fully integrated DC SQUID magnetometers

Temperature dependence of the main characteristics of integrated dc superconducting quantum interference device magnetometers based on niobium technology including an additional positive feedback circuit is reported. Temperatures above 4.2 K have been considered. A nonlinear temperature dependence of the spectral density of the field noise has been observed. The reported measurements show a slow increasing of the field noise up to temperatures of about 5 K, giving a considerable tolerance of the working temperature of niobium magnetometers in some innovative multichannel systems for magnetoencephalography.