Some Basic Facts about Semiconductor Materials

Semiconductor materials are a class of electronic materials that have semiconductor properties and are used to make semiconductor devices.

Characteristics of semiconductor materials

Semiconductor materials usually have a certain forbidden bandwidth and their electrical properties are susceptible to external conditions (e.g., light, temperature, etc.). Different conductive types of materials are prepared by doping with specific impurities. Impurities (especially heavy metal fast diffusion impurities and deep energy level impurities) have a particularly strong influence on the material properties. Therefore, semiconductor materials should be of high purity, which requires not only that the raw materials used to produce semiconductor materials should be of considerable purity, but also an ultra-clean production environment, with a view to minimizing impurity contamination in the production process. Most of the semiconductor materials are crystals, and semiconductor devices have high requirements for the crystal integrity of the materials. In addition, there are strict requirements for the uniformity of the various electrical parameters of the material.

Classification of semiconductor materials

Semiconductor materials can be classified according to their chemical composition, and amorphous and liquid semiconductors with special structures and properties are classified as a separate category. According to this classification method, semiconductor materials can be divided into elemental semiconductors, inorganic compound semiconductors, organic compound semiconductors, and amorphous and liquid semiconductors.

Elemental semiconductor

There are 11 kinds of semiconducting substances distributed in Group IIIA to Group IVA of the periodic table of elements. Among these 11 element semiconductors, only three elements, namely, Ge, Si, and Se, have been utilized. Ge and Si are still the two most widely used materials among all semiconductor materials.

Inorganic compound semiconductors

Inorganic compound semiconductors can be sub-divided into binary systems, ternary systems, and quaternary systems.

The binary system includes:

• Group IV-IV: Both SiC and Ge-Si alloys have the structure of sphalerite.
• Group III-V: It is composed of group III elements Al, Ga, In and group V elements P, As, Sb in the periodic table, and the typical representative is GaAs. They all have sphalerite structure, they are second only to Ge and Si in application, and have great development prospects.
• Ⅱ-Ⅵ group: Compounds formed by group II elements Zn, Cd, Hg and group VI elements S, Se, Te are some important optoelectronic materials. ZnS, CdTe, and HgTe have a sphalerite structure.
• Group I-VII: Compounds formed by group I elements Cu, Ag, Au and group VII elements Cl, Br, I, among which CuBr and CuI have sphalerite structure.
• Group V-VI: Compounds formed by Group V elements As, Sb, Bi and Group VI elements S, Se, Te have forms, such as Bi2Te3, Bi2Se3, Bi2S3, As2Te3, etc. are important thermoelectric materials.
• Oxides of group B and transition group elements Cu, Zn, Sc, Ti, V, Cr, Mn, Fe, Co, Ni in the fourth period are the main thermistor materials.
• Compounds formed by certain rare earth elements Sc, Y, Sm, Eu, Yb, Tm and Group V elements N, As or Group VI elements S, Se, Te. In addition to these binary compounds, there are solid solution semiconductors between them and elements or between them, such as Si-AlP, Ge-GaAs, InAs-InSb, AlSb-GaSb, InAs-InP, GaAs-GaP, etc. Studying these solid solutions can go a long way in improving certain properties of a single material or opening up new areas of application.

The ternary system includes:

• Composed of a group II and a group IV atom to replace two group III atoms in the III-V group. For example, ZnSiP2, ZnGeP2, ZnGeAs2, CdGeAs2, CdSnSe2, etc.
• Composed of one group I and one group III atom to replace two group II atoms in group II-VI, such as CuGaSe2, AgInTe2, AgTlTe2, CuInSe2, CuAlS2, etc.
• Composed of one group I and one group V atom to replace two group III atoms in the group, such as Cu3AsSe4, Ag3AsTe4, Cu3SbS4, Ag3SbSe4, etc.

Organic compound semiconductors

There are dozens of known organic semiconductors, such as naphthalene, anthracene, polyacrylonitrile, phthalocyanine, and some aromatic compounds.

Amorphous and liquid semiconductors

The biggest difference between this type of semiconductor and crystalline semiconductor is that it does not have a strictly periodic crystal structure.

What are the common semiconductor materials?

• Gallium Phosphide (GaP) (CAS 12063-98-8)
• Aluminium Gallium Indium Phosphide (AlGaInP) (CAS 163207-18-9)
• Gallium Arsenide Phosphide (GaAsP) (CAS 210471-34-4)
• Gallium Nitride (GaN) (CAS 25617-97-4)
• Silicon Carbide (CAS 409-21-2)
• Indium Gallium Nitride (InGaN)
• Aluminum Gallium Phosphide
• Aluminum Gallium Nitride (AlGaN)
• Aluminum Gallium Arsenide (AlGaAs)

Semiconductor Materials