On the Angular Dependence of InP High Electron Mobility Transistors for Cryogenic Low Noise Amplifiers in a Magnetic Field

The InGaAs-InAlAs-InP high electron mobility transistor (InP HEMT) is the preferred active device used in a cryogenic low noise amplifier (LNA) for sensitive detection of microwave signals. We observed that an InP HEMT 0.3-14GHz LNA at 2K, where the in-going transistors were oriented perpendicular to a magnetic field, heavily degraded in gain and average noise temperature already up to 1.5T. Dc measurements for InP HEMTs at 2K revealed a strong reduction in the transistor output current as a function of static magnetic field up to 14T. In contrast, the current reduction was insignificant when the InP HEMT was oriented parallel to the magnetic field. Given the transistor layout with large gate width/gate length ratio, the results suggest a strong geometrical magnetoresistance effect occurring in the InP HEMT. This was confirmed in the angular dependence of the transistor output current with respect to the magnetic field. Key device parameters such as transconductance and on-resistance were significantly affected at small angles and magnetic fields. The strong angular dependence of the InP HEMT output current in a magnetic field has important implications for the alignment of cryogenic LNAs in microwave detection experiments involving magnetic fields

Cryogenic Ultra-Low Noise InP High Electron Mobility Transistors

Indium phosphide high electron mobility transistors (InP HEMTs), are today the best transistors for cryogenic low noise amplifiers at microwave frequencies. Record noise temperatures below 2 K using InP HEMT equipped cryogenic low noise amplifiers (LNAs) were demonstrated already a decade ago. Since then, reported progress in further reducing noise has been slow. This thesis presents new technology optimization, modeling, measurements and circuit implementation for the cryogenic InP HEMT. The findings have been used to demonstrate a new record minimum noise temperature of 1 K at 6 GHz. The thesis considers aspects all the way from material, process and device design, to hybrid and monolithic microwave integrated circuit (MMIC) LNAs. The epitaxial structure has been developed for lower access resistance and improved transport characteristics. By investigating device passivation, metallization, gate recess etch, and circuit integration, low-noise InP HEMT performance was optimized for cryogenic operation. When integrating the InP HEMT in a 4-8 GHz 3-stage hybrid LNA, a noise temperature of 1.2 K was measured at 5.2 GHz and 10 K operating temperature. The extracted minimum noise temperature of the InP HEMT was 1 K at 6 GHz. The low-frequency 1/f noise in the 1 Hz to 1 GHz range and gain fluctuations in the 1Hz to 100 kHz range have been measured for six different types of HEMTs, and compared to two different SiGe heterojunction bipolar transistors (HBTs). The results showed that radiometer chop rates in the kHz range are needed for millimeter wave radiometers with 10 GHz bandwidth. A comparative study of GaAs metamorphic HEMTs (mHEMTs) and InP HEMTs has been performed. When integrated in a 4-8 GHz 3-stage LNA, the InP HEMT LNA exhibited 1.6 K noise temperature whereas the GaAs mHEMT LNA showed 5 K. The observed superior cryogenic noise performance of the InP HEMT compared to the GaAs MHEMT was related to a difference in quality of pinch-off as observed in I-V characteristics at 300 K and 10 K. To demonstrate the low noise performance of the InP HEMT technology, a 0.5-13 GHz and a 24-40 GHz cryogenic monolithic microwave integrated circuit (MMIC) LNA was fabricated. Both designs showed state-of-the-art low noise performance, promising for future radio astronomy receivers such as the square kilometer array

A 183-GHz Schottky diode receiver with 4 dB noise figure

Atmospheric science based on space-borne\ua0millimeter wave measurements require reliable and state-of-the art\ua0receivers. In particular, the water vapor line at 183.3 GHz\ua0motivates the development of sensitive mixers at this frequency.\ua0Traditional assembly techniques employed in the production of\ua0Schottky diode receivers involve flip-chip mounting and soldering\ua0of discrete dies, which prohibit the implementation of reliable and\ua0repeatable production processes. In this work, we present a\ua0subharmonic 183 GHz mixer implementing a repeatable assembly\ua0method using beamlead Schottky diodes. The mixer was\ua0integrated with a InP HEMT MMIC low noise intermediate\ua0frequency amplifier resulting in a record-low receiver noise\ua0temperature of 450 K at 1 mW of local oscillator power measured\ua0at room-temperature. The measured Allan time was 10 s and the\ua0third order local oscillator spurious power was less than -60 dBm.\ua0The proposed assembly method is of particular importance for\ua0space-borne missions but also applicable to a wide range of\ua0terahertz applications

Angular Dependence of InP High Electron Mobility Transistors for Cryogenic Low Noise Amplifiers under a magnetic field

This work addresses the angular dependence of DC properties in 100nm InP HEMT devices under the influence of applied static magnetic field at 2 K. When kept at an angle 90o towards a magnetic field of 14 T, the maximum output drain current Ids was reduced more than 99 %. A rotation sweep of the transistor revealed a strong angular and B-field dependence on Ids. This was correlated with a reduction in dc transconductance and increase in on-resistance of the transistor. The RF properties of the transistor were tested by measuring an 0.3-14 GHz InP HEMT MMIC low-noise amplifier (LNA) at 2 K kept at an angle 90o towards a magnetic field up to 10 T. The gain and noise temperature were strongly decreased and increased, respectively, already below 1 T. The results show that precise alignment of the cryogenic InP HEMT LNA is crucial in a magnetic field. Even a slight mis-orientation of a few degrees leads to a strong degradation of the gain and noise temperature

Phonon black-body radiation limit for heat dissipation in electronics

Thermal dissipation at the active region of electronic devices is a fundamental process of considerable importance. Inadequate heat dissipation can lead to prohibitively large temperature rises that degrade performance and intensive efforts are under way to mitigate this self-heating. At room temperature, thermal resistance is due to scattering, often by defects and interfaces in the active region, that impedes the transport of phonons. Here, we demonstrate that heat dissipation in widely used cryogenic electronic devices instead occurs by phonon black-body radiation with the complete absence of scattering, leading to large self-heating at cryogenic temperatures and setting a key limit on the noise floor. Our result has important implications for the many fields that require ultralow-noise electronic devices

Mean first-passage times for solvated LiCN isomerization at intermediate to high temperatures

The following article appeared in The Journal of Chemical Physics 156 (2022): 034103 and may be found at https://aip.scitation.org/doi/full/10.1063/5.0065090The behavior of a particle in a solvent has been framed using stochastic dynamics since the early theory of Kramers. A particle in a chemical reaction reacts slower in a diluted solvent because of the lack of energy transfer via collisions. The flux-over-population reaction rate constant rises with increasing density before falling again for very dense solvents. This Kramers turnover is observed in this paper at intermediate and high temperatures in the backward reaction of the LiNC ⇌ LiCN isomerization via Langevin dynamics and mean first-passage times (MFPTs). It is in good agreement with the Pollak-Grabert-Hänggi (PGH) reaction rates at lower temperatures. Furthermore, we find a square root behavior of the reaction rate at high temperatures and have made direct comparisons of the methods in the intermediate- and high-temperature regimes, all suggesting increased ranges in accuracy of both the PGH and MFPT approache

Low noise 874 GHz receivers for the international submillimetre airborne radiometer (ISMAR)

We report on the development of two 874 GHz receiver channels with orthogonal polarizations for the international submillimetre airborne radiometer. A spline horn antenna and dielectric lens, a Schottky diode mixer circuit, and an intermediate frequency (IF) low noise amplifier circuit were integrated in the same metallic split block housing. This resulted in a receiver mean double sideband (DSB) noise temperature of 3300 K (minimum 2770 K, maximum 3400 K), achieved at an operation temperature of 40 C and across a 10 GHz wide IF band. A minimum DSB noise temperature of 2260 K at 20 C was measured without the lens. Three different dielectric lens materials were tested and compared with respect to the radiation pattern and noise temperature. All three lenses were compliant in terms of radiation pattern, but one of the materials leads to a reduction in a noise temperature of approximately 200 K compared to the others. The loss in this lens was estimated to be 0.42 dB. The local oscillator chains have a power consumption of 24W and consist of custom-designed Schottky diode quadruplers (5% power efficiency in operation, 8%-9% peak), commercial heterostructure barrier varactor (HBV) triplers, and power amplifiers that are pumped by using a common dielectric resonator oscillator at 36.43 GHz. Measurements of the radiation pattern showed a symmetric main beam lobe with full width half maximum <5 and side lobe levels below 20 dB. The return loss of a prototype of the spline horn and lens was measured using a network analyzer and frequency extenders to be 750-1100 GHz. Time-domain analysis of the reflection coefficients shows that the reflections are below 25 dB and are dominated by the external waveguide interface