Band Gap Vs. Lattice Constants Diagram For Hexagonal Nitride Lab Analysis

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Figure1.3: Band gap vs lattice constants diagram for hexagonal nitride compounds. The typical of measured band gap bowing for ternary alloys AlGaN and InGaN is shown by the solid line track[21].
1.4. Unique Material properties of Gallium Nitride:
The unique material properties of GaN engraves it as an prominent semiconductor material for many electronic and optoelectronic devices[18].
• The wide and direct energy band gap sorts GaN as an appropriate materials for device fabrication in the field of optoelectronics emitters (LEDs and diodes lasers) and detectors.
• Moreover the higher thermal stability along with the wide energy band gap makes GaN beneficial for high-temperature (HT) and high power electronics applications. It implies that GaN power devices reduces the high cost processing steps related with optimized complicated designed structures to
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Equations (1.4) and (1.5) can be combined to obtain the equation for piezoelectric polarization as,
P_pz=2 (a_s-a_o)/a_o (e_31-c_13/c_33 e_33) (1.6)
The total polarization P tot is calculated by summing together the two polarization components:
P_tol =〖 P〗_sp + P_pz . (1.7)
Total polarization in InGaN and AlGaN as a function of molar fraction is plotted in Fig. 1.6, assuming unstrained GaN is used as substrate. These polarization effects were found to be much stronger in c-face nitrides than in other III-V compounds. With the growth direction along the c-axis, both types of polarization add up to the surface charge density can be given by, qσ_2D=P_sp+P_pz=P_sp+2 (a_s-a_o)/a_o (e_31-c_13/c_33 e_33 ) (1.8)
Table 1.2: Calculated values for spontaneous polarization and piezoelectric constants in group III nitrides[28].
Paramters Materials GaN InN AlN
Spontaneous polarization, Psp (Cm−2 ) −0.034 −0.042

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