Substrates for Semiconductor Thin Film Growth

  • With wide direct bandgap(3.4 eV), strong atomic bonds, high thermal conductivity and excellent radiation resistance, GaN is not only short-wave-length optoelectronic material, but also a well alternate material for high temperature semiconductor devices. Based on the stabile physical and chemical properties, GaN is suitable for LED applications (blue, green, UV-light), ultraviolet detectors and optoelectronic high-power and high-frequency devices. 
  • ScAlMgO4, a newly developed substrate material for GaN and ZnO heteroepitaxy. So far, with the minimum lattice mismatch, it has the best lattice match with GaN and ZnO and is an ideal substrate material for GaN and ZnO epitaxy. The lattice mismatch of the thermal expansion coefficient at axis with GaN, ZnO epitaxial films is much better than sapphire and silicon.
  • MgAl6O10 is substrate material for GaN and ZnO epitaxial film. Compared with MgAl2O4, MgAl6O10 has less lattice mismatch and thermal expansion mismatch with GaN (the lattice mismatch is -11.5%, thermal expansion mismatch is 2.2×10-6/℃). With low melt point, MgAl6O10 is more suitable to be the substrate material for bigger size and higher quality crystals. In addition, Experimental results show the GaN and ZnO devices prepared on MgAl6O10 have better light-emitting than on sapphire.
  • Because the dielectric constant and loss microwave band of MgO single crystal is very small, and the large size MgO substrate (diameter of 2 inches and larger) can be obtained, it has currently become an important industrial HTS thin monocrystalline substrate. MgO is an excellent single crystal substrate for thin films of Ferro magnetic, Photo-electronic, semiconductor and high Tc superconductor applications. There is also a growing amount of interest in using MgO substrates for the III to V elements, and in research studying the epitaxial effects of substrates on the crystallization of polymers. Other applications include the deposition of ferro electric thin film coatings on magnesium oxide substrates. And there are also growing applications for MgO in the field of plasma display panel (PDP) technology.
  • Al2O3 crystals or Sapphire is a multi-function crystal materials with excellent properties: good thermos-stability, high thermal conductivity, high hardness, high transmission at infrared wavelength rang and excellent chemical stability. Sapphire is widely used in industrial, defense and security and scientific research fields. sapphire is also an important substrate materials for high temperature superconductivity applications, it can be used for film growth of Y-series, La-series, and it is also used to grow the superconductivity film of MgB2.
  • LiAlO2 single crystal is a potential substrate for III-V nitride thin films, the lattice mismatch between LiAlO2 and GaN is only 1.4%. LiAlO2 substrate was stable enough to stand the high-temperature reductive atmosphere. Single-oriented GaN film can be grown on LiAlO2 substrates without using low-temperature buffer layers. Hangzhou Shalom EO can supply LiAlO2 wafer up to 2” in diameter.
  • ZnO has the potential to become the substrate material of choice for GaN. Like GaN, it has a wurtzite structure, with lattice constants closely matches to GaN (a=3.249, c=5.205). The lattice mismatch between ZnO and GaN isε=0.017. Perhaps most important is that it is a soft compliant material which is believed to take up the lattice stress in preference to the growing GaN layer. It suffers from the drawback that it dissociates in ammonia at temperatures above 600°C. With its wide bandgap, Zinc Oxide is proved very useful in optical applications as well as many high speed electronics. ZnO is also used as a substrate for epitaxial growth.
  • Gallium Arsenide (GaAs) is a compound of the elements gallium and arsenic. It is a III-V direct bandgap semiconductor with a Zinc blende crystal structure. Gallium Arsenide is used in the manufacture of devices such as microwave frequency integrated circuits, monolithic microwave integrated circuits, infrared light-emitting diodes, laser diodes, solar cells and optical windows. GaAs is often used as a substrate material for the epitaxial growth of other III-V semiconductors including indium gallium arsenide, aluminum gallium arsenide and others. And this kind of substrates has good performance under high frequency, high temperature and low temperature, low noise and high radiation tolerance.
  • Single Crystal Silicon for solar energy applications includes p-type and n-type silicon. Ultra high purity silicon is used in the semiconductor industry as a result of its semiconducting properties. Silicon is also used as an alloying element in the manufacture of certain alloys (e.g. ferrosilicon, an alloy of iron and silicon which is used to introduce silicon into steel and cast iron). Single Crystal Silicon is generally immediately available in most volumes.

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