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Hall measurements have been made on epitaxially grown, zinc-doped gallium phosphide, from which the gallium arsenide substrate had been removed. The measurements were made in the temperature range from 300° to 4°K on samples whose room-temperature carrier concentration varied from 7×1015 to 7×1018 cm−3. Using both van der Pauw and conventional Hall techniques on those samples which show a high degree of compensation, the variation of the ionization energy of zinc with concentration was determined. Room-temperature hole mobility varied from 60 to 100 cm2· V−1· sec−1. These observed hole mobilities are in good agreement with the calculated values of mobility due to reduced scattering by acoustical and optical phonons, and are shown to be too small to be accounted for by the mechanism of impurity scattering below 100°K. Resistivity measurements made in the temperature range 77°–4.2°K show that in the impurity band conduction range, gallium phosphide behaves in a manner similar to impure germanium.

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Tunneling junction diodes were designed specifically for use as miniature pressure gauges. They were fabricated from arsenic doped germanium of resistivity 0.001 Ω-cm and tested under hydrostatic pressures up to 700 kg/cm2. Gauge factors of 350 were achieved and the change in ``peak'' current with pressure was shown to be comparable with that of Esaki diodes. These diodes differ from ordinary tunnel diodes in that the peak-to-valley ratio has been reduced to 1 or less by increasing the excess and diffusion currents via high temperature alloying and increased alloying times. A negative resistance region appears only at low temperatures. This type of flat-characteristic, two-terminal device is useful as a variable range pressure gauge by utilizing the pressure dependence of the tunneling current. These diodes have the advantage that they need not satisfy the strict stability requirements of the amplifier mode as does the tunnel diode when it is used in this manner; furthermore, bulky low inductance mounting is no longer needed. It is now possible to take full advantage of the extremely small size of these diodes, the working area of which may be as small as 0.076 mm in diam.