STUDY OF HIGH FREQUENCY LATTICE VIBRATION IN INDIUM NITRIDE FOR VARIOUS APPLICATIONS.

The piezoelectric properties of various crystals at DC and microwave frequencies are utilized in numerous devices and applications. However, high-frequency (optical) piezoelectric lattice vibrations in crystals, where ionic polarization dominates, are rarely studied and applied. Using classical dispersion theory, a mathematical expression relating the dielectric constant (ε_ii) and piezoelectric coefficient (d_ii) is established for the widely accepted piezoelectric material Indium Nitride (InN). This relation is further used to study high-frequency lattice vibrations in InN, demonstrating that an electric field at high frequencies (optical) can produce acoustic phonons in phase, thereby enabling control over the material's thermal conductivity through the inverse piezoelectric effect. This ability to modulate thermal conductivity could enhance the efficiency of optoelectronic devices, such as laser diodes (LDs) and lightemitting diodes (LEDs), where InN is used as a quantum well. Since it is challenging to measure (d_ii) directly through experimental techniques, the established relation can be utilized to determine it using infrared (IR) reflection techniques. A fairly good agreement is observed between the experimental and computed values of d_ii, validating the theoretical model. [ABSTRACT FROM AUTHOR]