MOSFET operating temperature

Diamond and Refractory Ceramic Semiconductors. Ceramic thin films of diamond, sihcon carbide, and other refractory semiconductors (qv), eg, cubic BN and BP and GaN and GaAlN, are of interest because of the special combination of thermal, mechanical, and electronic properties (see Refractories). The majority of the research effort has focused on SiC and diamond, because these materials have much greater figures of merit for transistor power and frequency performance than Si, GaAs, and InP (13). Compared to typical semiconductors such as Si and GaAs, these materials also offer the possibiUty of device operation at considerably higher temperatures. For example, operation of a siUcon carbide MOSFET at temperatures above 900 K has been demonstrated. These devices have not yet been commercialized, however. 

The latter direction was initiated by Danielsson et al. (1979), who combined immobilized hydrogenase with a hydrogen gas-sensing MOSFET. Since the MOSFET requires a high operational temperature it was separated from the enzyme layer. Caras and Janata (1980) directly integrated the microelectronic sensor and the immobilized... 

Briand, D., Wingbrant, H., Sundgren, H., van der School, B., Ekedahl, L.-G., Lundstrom, I. and de Rooij, N. F. (2003), Modulated operating temperature for MOSFET gas sensors Hydrogen recovery time rednetion and gas discrimination , Sens. Actuators B, 93,276-85. 

The QCM sensors [5] have gained popularity because they are operated at room temperature and allow combinations of selective layers different to those of MOS, MOSFET and PC sensors. The QCM measures physical mass of the analyte by recording the change in frequency of a quartz crystal when the analyte binds to it. Layers of gas chromatographic stationary phases and natural or synthetic lipids can discriminate between alcoholic drinks, perfume and flavor odorants. 

Metal oxide semiconductor field effect transistors (MOSFETs) constitute other materials with applicability in the development of biosensors. Usually, a MOSFET structure consists of a metal gate on top of an oxide layer, tyqjically Si02 [189]. The catalytic properties of these sensors depend upon the type of the gate metal as well as the temperature at which the MOSFET is operated. The most used catalytic metals used as gate materials are Pd (is a good... 

In attempting to generally reduce parasitics and their associated losses, we may notice that these are often dependent on various external factors — temperature for one. Some losses increase with temperature — for example the conduction loss in a mosfet. And some may decrease — for example the conduction loss in a bjt (when operated with low currents). Another example of the latter type is the ESR-related loss of a typical aluminum electrolytic capacitor, which also decreases with temperature. On the other hand, some losses may have rather strange shapes. For example, we could have an inverted bell-shaped curve — representing an optimum operating point somewhere between the two extremes. This is what the core loss term of many modern ferrite materials (used for inductor cores) looks like — it is at its minimum at around 80 to 90°C, increasing on either side. 

Different types of SiC Field Effect Transistors, Metal Oxide Semiconductor Transistors (MOSFETs), Metal Semiconductor Field Effect Transistors (MESFETs), and Junction Field Effect Transistors (JFETs) compete for future applications in high temperature and harsh environment electronics. This Datareview details these various types of FETs, the structures used and the performances obtained. Interesting recent developments and potential applications, such as FET integrated circuits, a hybrid operational amplifier and an inverter circuit are also outlined. 

The first SiC MOSFETs were fabricated by Suzuki et al [1] in 3C-SiC. At the present time, SiC MOSFET research is carried out by several groups, including Cree Research [2-4] and Westinghouse [5]. Enhancement mode and depletion mode (3-SiC MOSFETs have been fabricated by Palmour et al [3]. Enhancement mode devices with 5 pm gate lengths had a maximum transconductance (gm) of 0.46 mS mm 1 at room temperature (see FIGURES 1 and 2). The devices were operational up to 823 K. 

Recently, Cree Research Inc. reported on the first p-channel 6H-SiC MOSFET [6]. The device structure and output characteristics are shown in FIGURES 8 and 9, respectively. The device current and transconductance are very small (76 pA mm 1 at 40 V of drain bias and 16 pS mm 1, respectively, for a 7 pm gate length device). The performance of this device was limited by a large parasitic series resistance. Nevertheless, even these preliminary results show the feasibility of SiC CMOS technology, capable of operating at elevated temperatures. 

Although the PFA was designed to run at 20K, operation of the FPA has been demonstrated all the way to liquid helium temperatures (4K). This means that the array can be used in a liquid helium dewar with no active temperature control, greatly simplifying dewar construction. Of course, the detector dark current does not get significantly better at temperatures below 30K, and the noise of the multiplexer will be somewhat higher due to the increase in MOSFET noise. Nonetheless, some applications will benefit from this extra capability. 

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