Compound Semiconductor Materials

•Compound semiconductor materials are mostly prepared either from the combinations Group III and Group V elements or from the combinations of Group Hand Group elements

•Compounds prepared from two elements is known as binary compounds where as prepared from three elements is known as ternary compounds.

•The wide variety of electronic and optical properties of semiconductors enable greater flexibility in the design and manufacturing of electronic and optoelectronic device.

•As mentioned in Table 1.1.1, there are numerous semiconductor materials. Among these, is used for the majority of semiconductor devices like rectifiers, transistors, SCRs, UIT resistors, thermistors and integrated circuits are usually made of Si.

•Compound semiconductors are mostly used in devices requiring the emission or absorption of ligh

•For example, light emitting diodes (LEDs) are generally fabricated from compounds like GaAs, GaP and mixed compounds like GaAsP.

•For television screen fluorescent materials are used which are generally H-VI compound semiconductors like ZnS. Light sensors are commonly made with InSb, CdSe, or other compounds of lead like PbTe, PbSe.

•Si and Ge are also used widely as nuclear radiation and Infrared detectors. Microwave device, Gunn diode, semiconductor laser are commonly fabricated from compound semiconductor like GaAs, InP.

•Hence, the wide range of semiconductor materials offers considerable variety in properti and provides engineers with much flexibility in the design of electronic functions. Compound semiconductors are widely used in high speed semiconductor devices.

• The electronic and optical properties of semiconductor materials are strongly affected due to doping of impurities in precisely controlled amounts. This process of doping impurities causes wide variation in the conductivities of the to semiconductor and even after the conduction processes from conduction by negative charge carriers to positive charge carriers.

•An impurity concentration variation in ppm (parts per million) order can change the property of silicon from poor conductor to a good conductor of electricity. As even slight variation of impurities produce dramatic changes in electrical and optical properties of semiconductors, so details study about the specific arrangement of atoms in each semiconductor is required to use it properly for semiconductor device applications. 

•The most important feature which distinguishes semiconductor from conductor and insulators is its energy band gap which is of the order of (1-2) eV. This energy band gap can easily overcome by using visible-IR light as and when required.

•For example, the energy band gap of GaAs is about 1.43 eV that corresponds to light wavelength in the near infrared and GaP has an energy gap 2-3 eV, which corresponds to wavelength in the green portion of the visible spectrum.

• As the semiconductors (Compound) are available in the wide range of energy band gap, so light emitting diodes (LEDs) and semiconductor laser can be designed with wavelengths over a broad range of spectrum i.e. Infra-red to visible range of the spectrum. Also compound semiconductors are used to design efficient solar cells.