In this study, we investigated the microstructure and optical properties of hexagonal GaN (h-GaN) films grown by high-temperature pulsed laser deposition (PLD) on Si(100) and Si(111) substrates. The growth mechanism, crystallization, and surface morphology of h-GaN deposition on both Si(100) and Si(111) substrates were monitored by transmission electron microscopy (TEM) and scanning electron microscopy at various times in the growth process. Our results indicated that the h-GaN grown on Si(111) has better crystalline structure and optical properties than that on Si(100) owing to the smaller mismatch of the orientations of the Si(111) substrate and h-GaN film. On the Si(100) substrate, the growth principles of PLD and N2 plasma nitridation are the main contributions to the conversion of the cubic GaN into h-GaN. Moreover, no significant Ga–Si meltback etching was observed on the GaN/Si surface with the PLD operation temperature of 1000 °C. The TEM images also revealed that an abrupt GaN/Si interface can be obtained because of the suppression of substrate–film interfacial reactions in PLD.
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