Semiconductor Photovoltaic Effect and Devices

Abstract

The photovoltaic effect is the generation of a voltage due to optical excitations when a semiconductor is illuminated at the electrodes or at internal barriers or p-n junctions. The specific effect that will be the subject of these lectures is the voltage developed when a semiconductor body containing a p-n junction is exposed to optical illumination. Two possibilities exist and both will be considered; one, when one ohmic contact is on the p-region and the second ohmic contact is on the n-region of the body; and two, when both contacts are on the same type of material. These are known as the transverse photovoltaic effect and the lateral photovoltaic effect, respectively. These are designated in Figure 1. The transverse photovoltaic effect is commonly used in solar energy converters, photodiodes, radiation detectors, special types of null detectors and tracking detectors, etc. The lateral photovoltaic effect is used at present only in what is commercially known as the radiation tracking transducer. For most applications, the devices are operated in the steady state condition with the radiation continuously falling on the devices (or with the radiation intensity changing slowly compared to the time constants of the device). Thus most of the discussion will be devoted to the steady state solutions of the fundamental relations.