ABSTRACT
A piece of germanium, one part of which is a p-type semi-conductor and the other part is n-type, forms at the junction a barrier of high resistance and photosensitivity. Light which is effective photoelectrically is practically entirely absorbed within a very small thickness (<10–3cm). In samples having a thickness of a fraction of a millimetre and more only a part of the junction area is activated and generates an electromotive force (EMF) VP . This EMF is in series with r, the resistance of the activated part of the barrier. In parallel with this combination are the resistance R of the unactivated part of the barrier and the capacitance C of the barrier. The barrier is in series with the bulk resistance of the sample, which is comparatively negligible, and the input resistance Re of the amplifier. To obtain maximum voltage Re should be large compared with R. figure 1.1 shows curves of measured voltage versus Re for two temperatures. The experiments reported below were made with sufficiently large Re so that its effect can be neglected. Effect of external load resistance on photovoltage https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315793245/fba3410f-a7b2-4207-80b4-b0645bac91bb/content/fig2_1_1.tif"/>
