Introduction to semiconductor ceramics

Through semiconductorization measures, ceramics have semiconductive grains and insulating (or semiconductor) grain boundaries, thus showing strong interface barriers and other semiconductor properties.

There are two main methods for semiconductorization of ceramics: forced reduction method and donor doping method (also known as atomic valence control method). Both methods form defects such as ion vacancies in the crystals of ceramics, thereby providing a large number of conductive electrons, making the grains in the ceramics become a certain type (usually N-type) semiconductor. The interlayer between these grains is an insulating layer or another type (P-type) semiconductor layer.

There are many types of semiconductor ceramics, including various negative temperature coefficient thermistors made using the properties of the grains in semiconductor ceramics; semiconductor capacitors, ZnO varistors, BaTiO3 positive temperature coefficient thermistors, CdS/Cu2S solar cells made using the properties of grain boundaries; and various ceramic hygroscopic resistors and gas sensitive resistors made using surface properties. Table 2 lists typical semiconductor ceramics for sensors.

CdS/Cu2S photoelectric ceramics are different from the semiconductor ceramics listed in the table above that use the properties of the insulating grain boundary layer. They use the photovoltaic effect of the PN heterojunction between the N-type CdS and P-type Cu2S grain boundary layers. Ceramic solar cells made of them can be used as power sources for unmanned stations and as photoelectric coupling devices in electronic instruments.