26
3 Properties and Testing of Group III-Nitride LED Materials
Table 3.4 Common acceptor
doping in wurtzite GaN
Acceptor Substitutional site Impurity ionization energy (eV)
V Ga
Ga vacancy
0.14
Mg
Ga site
0.14–0.21
Si
N site
0.19
Zn
Ga site
0.21–0.34
Hg
Ga site
0.41
Cd
Ga site
0.55
Be
Ga site
0.7
Li
Ga site
0.75
C
N site
0.89
Ga
N site
0.59–1.09
activation rate of Mg is only 2 × 10
−4 , it brings the hope to the possibility of Mg
doping. In 1992, S. Nakamura utilized annealing at 700 °C in nitrogen atmosphere to
active Mg atoms. This lead to a hole concentration of 3 × 10
17 /cm
3 [14]. Up to now,
the Mg doping, in combination with the annealing process, has become a commonly
used p-type standard process for GaN. It is generally believed that Mg doping in
GaN materials will affect the material quality due to the large Mg atoms. However,
some research results show that Mg doping is beneficial to the reduction of V-type
defects in GaN materials and improves the crystal quality of GaN materials.
3.4 Test and Analysis of the Properties of Group III Nitride
Materials
The performance of the device is directly affected by the quality of the material. The
characterization and analysis of the material can reflect the quality of the material
and guide the adjustment of the material growth process. In this section, we briefly
describe the common analytical methods for testing the properties of nitride materials.
3.4.1 Structural and Morphological Analysis
The structure and morphology of crystals are fundamental research in the application of materials. Especially in semiconductors, the crystal structure determines
the band structure of the material. The band structure of the material is the main
factor to be considered for light-emitting device. Since the melting temperature of
the GaN material is higher than the decomposition temperature, the preparation of
the single crystal is not as easy as that of the first generation and the second generation semiconductors. As such, the quality of the crystal is not very high. In this case,
3 Properties and Testing of Group III-Nitride LED Materials
Table 3.4 Common acceptor
doping in wurtzite GaN
Acceptor Substitutional site Impurity ionization energy (eV)
V Ga
Ga vacancy
0.14
Mg
Ga site
0.14–0.21
Si
N site
0.19
Zn
Ga site
0.21–0.34
Hg
Ga site
0.41
Cd
Ga site
0.55
Be
Ga site
0.7
Li
Ga site
0.75
C
N site
0.89
Ga
N site
0.59–1.09
activation rate of Mg is only 2 × 10
−4 , it brings the hope to the possibility of Mg
doping. In 1992, S. Nakamura utilized annealing at 700 °C in nitrogen atmosphere to
active Mg atoms. This lead to a hole concentration of 3 × 10
17 /cm
3 [14]. Up to now,
the Mg doping, in combination with the annealing process, has become a commonly
used p-type standard process for GaN. It is generally believed that Mg doping in
GaN materials will affect the material quality due to the large Mg atoms. However,
some research results show that Mg doping is beneficial to the reduction of V-type
defects in GaN materials and improves the crystal quality of GaN materials.
3.4 Test and Analysis of the Properties of Group III Nitride
Materials
The performance of the device is directly affected by the quality of the material. The
characterization and analysis of the material can reflect the quality of the material
and guide the adjustment of the material growth process. In this section, we briefly
describe the common analytical methods for testing the properties of nitride materials.
3.4.1 Structural and Morphological Analysis
The structure and morphology of crystals are fundamental research in the application of materials. Especially in semiconductors, the crystal structure determines
the band structure of the material. The band structure of the material is the main
factor to be considered for light-emitting device. Since the melting temperature of
the GaN material is higher than the decomposition temperature, the preparation of
the single crystal is not as easy as that of the first generation and the second generation semiconductors. As such, the quality of the crystal is not very high. In this case,