Chapter 3
Properties and Testing of Group
III-Nitride LED Materials
The group III nitride semiconductor material mainly includes the compounds GaN,
AlN, InN, and their alloys such as AlGaN, GaInN, AlInN, and AlGaInN. The band
gap (0.7~6.03 eV) of these materials with the different components covers the whole
visible spectrum, which makes the nitride semiconductor materials attractive for a
range of applications. However, due to the nature of the nitride material, there are
many difficulties in the development process that need further research. This chapter
mainly introduces the basic properties of nitride semiconductor materials, including
crystal structure, band structure, polarization effect, doping, crystal defects and
certain characterization methods to measure the physical properties of the materials.
3.1 Crystal Structure and Band Structure of Group III
Nitride
3.1.1 Crystal Structure
The III-nitride semiconductor material has three crystal structures: hexagonal
wurtzite, cubic sphalerite, and sodium chloride-type rock salt. The rock salt structure
is generally formed only under extreme high pressure and will not be specifically
introduced here.
The sphalerite structure is a cubic close-packed structure formed by nesting 1/4
diagonal lengths of two face-centered cubic lattice structures along the diagonal line
[1]. A unit cell contains 8 atoms, of which 4 are Ga atoms and 4 are N atoms. This
structure belongs to the thermodynamic metastable structure and is mostly prepared
at low temperatures.
The wurtzite structure is a hexagonal symmetry structure formed by two hexagonal
dense stack lattices translating 3/8 cell heights along the c-axis. A unit cell contains
© Science Press and Springer Nature Singapore Pte Ltd. 2020
J. Li et al., III-Nitrides Light Emitting Diodes: Technology and Applications,
Springer Series in Materials Science 306,
https://doi.org/10.1007/978-981-15-7949-3_3
19
Properties and Testing of Group
III-Nitride LED Materials
The group III nitride semiconductor material mainly includes the compounds GaN,
AlN, InN, and their alloys such as AlGaN, GaInN, AlInN, and AlGaInN. The band
gap (0.7~6.03 eV) of these materials with the different components covers the whole
visible spectrum, which makes the nitride semiconductor materials attractive for a
range of applications. However, due to the nature of the nitride material, there are
many difficulties in the development process that need further research. This chapter
mainly introduces the basic properties of nitride semiconductor materials, including
crystal structure, band structure, polarization effect, doping, crystal defects and
certain characterization methods to measure the physical properties of the materials.
3.1 Crystal Structure and Band Structure of Group III
Nitride
3.1.1 Crystal Structure
The III-nitride semiconductor material has three crystal structures: hexagonal
wurtzite, cubic sphalerite, and sodium chloride-type rock salt. The rock salt structure
is generally formed only under extreme high pressure and will not be specifically
introduced here.
The sphalerite structure is a cubic close-packed structure formed by nesting 1/4
diagonal lengths of two face-centered cubic lattice structures along the diagonal line
[1]. A unit cell contains 8 atoms, of which 4 are Ga atoms and 4 are N atoms. This
structure belongs to the thermodynamic metastable structure and is mostly prepared
at low temperatures.
The wurtzite structure is a hexagonal symmetry structure formed by two hexagonal
dense stack lattices translating 3/8 cell heights along the c-axis. A unit cell contains
© Science Press and Springer Nature Singapore Pte Ltd. 2020
J. Li et al., III-Nitrides Light Emitting Diodes: Technology and Applications,
Springer Series in Materials Science 306,
https://doi.org/10.1007/978-981-15-7949-3_3
19