A new approach to the measurement of h.f. power by Hall effect in a semiconductor

It is well known that the Hall effect in a semiconductor situated in an electromagnetic field is determined by the Poynting vector and is therefore a measure of the net power transmitted through the semiconductor. In previous work the application of this technique to h.f. wattmeters has been discussed on the basis that the whole of the power entering the load was passed through a thin slice of the semiconducting crystal in which the Hall effect was measured. In the present analysis, which conforms much more closely to a practical arrangement when using high-conductivity semiconductors, most of the power is transmitted via the space surrounding the crystal, whilst the power entering the crystal itself is almost wholly absorbed. A very thin wafer of indium antimonide or indium arsenide is thus placed edge-on to the incident electromagnetic wave and picks up a pure displacement current from the surrounding air. No special phasing arrangements appear to be necessary, and the only wires attached to the crystal are those required for measuring the Hall e.m.f. A group of crystals connected in cascade can be used to increase the sensitivity of the device. It is concluded that with careful screening of the Hall leads a simple monitor for determining the power transmitted in any given direction through space can be readily developed from an arrangement of this kind.