Lithium Gallate (LiGaO2) Crystals and Substrates

Lithium Gallate or LiGaO2 represents a promising alternative to conventional substrates for GaN due to its lattice constants, chemical and thermal stability, and potential ease of separation. Since the lattice mismatch between hexagonal GaN and LiGaO2 is only about 0.9%, this substrate is considered to be one of the most promising candidates for hexagonal GaN growth. LiGaO2 is orthorhombic with cell a=5.402 A,b=6.372 A, and c=5.007 A belonging to the space group Pna21. This means that LiGaO2 is polar crystal with respect to the c-axis. From these cell dimensions, the average value of its lattice mismatch to hexagonal GaN is estimated to be about ~1%. LiGaO2 provides a good thermal match and has a high transparency in the visible and ultraviolet regions. Therefore,  LiGaO2 is expected to be a promising substrate material for the growth of high quality hexagonal GaN thin film.