Deep Cryogenic Temperatures Research Articles

SiGe and Ge Cryogenic Power Transistors

We have undertaken development of power semiconductor devices based on SiGe and Ge, intended for operation over a wide temperature range, from room temperature down to deep cryogenic temperatures, ~30 K (~ -240{degree sign}C). We summarize results for Ge diodes (~10 A/400 V), Ge junction field-effect transistors (Ge JFETs, ~0.5 A/30 V), Ge metal-insulator field-effect transistors (Ge MIS-FETs ~1 A/20 V) and SiGe heterojunction bipolar transistors (SiGe HBTs, ~10 A/50 V). As a practical demonstration, we have used SiGe HBTs and SiGe diodes as the active devices in 100-W power-conversion circuits, operating from room temperature down to ~30 K (~ -240{degree sign}C) with increased efficiency as temperature de-creases. Our developments demonstrate the potential of alternative semiconductor materials to provide excellent performance for power applications down to deep cryogenic temperatures.

The Influence of Post-Quenching Deep Cryogenic Treatment on Tempering Processes and Properties of D2 Tool Steel. Studies of Structure, XRD, Dilatometry, Hardness and Fracture Toughness

A significant increase in durability of cryogenically treated tools after quenching was reported by a number of publications [1, 2]. As research studies show [4, 5, 6, 7], the main reason for this is the kind of carbides precipitated during tempering at temperature range of 150 –200 0C, which is different than in the case of conventional treatment. These carbides are finer and more evenly distributed in the matrix of steel. The number of carbides is higher than in conventionally treated steels because of higher fraction of martensite in cryogenically treated steels produced by retained austenite transformation at cooling to deep cryogenic temperatures. The number of carbides precipitated from martensite at low temperatures of tempering is proportional to shrinkage produced at the same temperatures of tempering. Calculations on the basis of dilatometric experiments show that the shrinkage difference between the same D2 steel cryogenically and conventionally treated is higher than that which results from the increased fraction of martensite in cryogenically treated steel. The XRD studies of cryogenically treated steel show a presence of two kinds of martensites differing in tetragonality. Low temperature tempering of cryogenically treated steel produced two types of carbides – ε carbide and η carbide. The conventionally treated steel consists of one kind of tetragonal martensite and one kind of carbide - the ε carbide. The hardness of cryogenically treated samples was somewhat higher than in conventionally treated ones, while fracture toughness of conventionally treated samples was somewhat higher than in cryogenically treated ones. The results obtained were discussed in reference to literature data.

Interferential scanning grating position sensor operating in space at 4 K.

An interferential position sensor for operation in space at a deep cryogenic temperature (4 K) is derived from a commercial sensor. The application is for the Spectral and Photometric Imaging Receiver submillimetric imaging Fourier-transform spectrometer on the Herschel space telescope. This sensor is used to control the displacement of the interferometer's moving mirrors and to sample the interferograms. This development addresses the following points: minimization of the effects of cooling critical optical parts, introduction of a fully redundant focal plane, selection of optoelectronic components efficient at 4 K, and design of a cryogenic preamplifier.

Ge semiconductor devices for cryogenic power electronics - II

We have begun investigation and development of cryogenic semiconductor power devices (diodes, bipolar transistors and field-effect transistors) based on germanium. The motivation is NASA's interest in electronics that can operate down to deep cryogenic temperatures (as low as 30-40 K) for exploration of the outer planets and other Solar System bodies that present cold environments as well as for future space observatories. There are also potential applications related to cryogenic/superconducting motors and generators and power distribution and storage. We have characterized available Ge diodes and bipolar transistors at cryogenic temperatures and have begun examining MIS (metal-insulator-semiconductor) capacitors on Ge. Our investigations show that all these types of devices can operate from room temperature down to 20 K or lower.

The cryogenic operation of partially depleted silicon-on-insulator inverters

This paper describes the cryogenic operation of inverters fabricated in a partially depleted (PD) 1 /spl mu/m Silicon-on-Insulator (SOI) CMOS technology. As is shown, the floating-body effects like the kink effect degrade the static transfer characteristics considerably. Generally, the effects aggravate upon cooling. Additionally, at deep cryogenic temperatures, e.g., 4.2 K, typical low-temperature anomalies, which are related to the device freeze-out, cause hysteresis effects. Ways for improvement are discussed and compared: As is shown, the PD SOT inverter anomalies can be largely reduced by using the so-called twin-gate configuration.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

DC characteristics of gate-all-around (GAA) silicon-on-insulator MOSFETs at cryogenic temperatures

This paper describes the static I-V characteristics at cryogenic temperatures (77 K and 4.2 K) of so-called dual-gate Silicon-on-Insulator (SOI) MOSFETs, fabricated in the Gate-all-Around (GAA) technology. The n-channel devices are characterised by an increase of the threshold voltage and the transconductance upon cooling, which is observed both for the edge-channel component and for the primary drain current. It is shown that the devices suffer less from the hysteresis and transient effects, which have been reported before in standard SOI transistors. For the first time, the occurrence of the back-gate induced Multistable-Charge-Controlled-Memory (MCCM) effect in GAA devices is demonstrated at 4.2 K. The p-channel devices on the other hand show specific instabilities at deep cryogenic temperatures, which are related to the unexpected reduction of |V T |