It has been observed that the forward voltage drop, at constant forward current, of a GaAs diffused p-n junction varies almost linearly with temperature from 2.0°K to above 300°K. Since carrier ``freeze-out'' at low temperatures is not observed, these junctions make excellent cryometers. In addition, these diodes exhibit good repeatability on temperature cycling and an insensitivity to magnetic fields. The sensitivity of the devices measured near room temperature is ΔV/ΔT≈−3.5 mV/°C, If=0.1 μA; ΔV/ΔT≈−2.0 mV/°C, If=1.0 mA. The sensitivity decreases slowly toward lower temperatures and at liquid helium is −1.5 mV/°C and is essentially independent of current. This high and nearly uniform sensitivity over such a wide temperature range is unique among low temperature thermometers. The shape of the temperature-voltage characteristic, with current as a parameter, is explained quite satisfactorily for T>50°K by assuming that the device conducts primarily recombination-generation currents, according to the theory of Sah, Noyce, and Shockley. Below 50°K certain deviations from this theory occur, but the applicability of the devices to thermometry is not affected. It appears likely that these devices are capable of a temperature resolution of at least ±0.01°C over the entire range investigated, using ordinary current sources and precision potentiometers.

We have developed a novel triply modulated stimulated Raman gain spectrometer which reduces unwanted background effects by over 105. This has allowed the high resolution (Δν=1 cm−1) measurement of 20 Å of Si on sapphire with a signal-to-noise ratio of 100, with only 2 min of data collection. This sensitivity is several orders of magnitude larger than spontaneous Raman scattering.

We report measurements of the room-temperature drift velocity of holes along the (100) Si-SiO2 interface (drift direction [011]) as obtained by a time-of-flight technique. Our measured values range up to 60% higher than previously reported values at comparable tangential and normal electric fields. An empirical equation that fits the low-field mobility and the high-field velocity as a function of tangential and normal fields is presented.

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