Abstract
Gallium Nitride substrates are crucial for the production of reliable GaN-based devices with high current density: light emitting diodes and lasers, high-voltage diodes and transistors, and microwave high electron mobility transistors. However, the widespread use of GaN substrates is currently limited by their high price. To solve this problem, the Laser Slicing™process has been developed [1]: a method for lifting off a thin GaN film from the bulk GaN substrate. The demonstrated Laser Slicing™process does not require any special release layers and can be used both for lifting off pure GaN films and for lifting off GaN films with device structure. The application of such a process allows to reuse the expensive bulk GaN substrate many times and thereby reduce the cost of the devices. The proposed method is based on the effect of GaN decomposition caused by an ultrashort laser pulse focused inside a bulk GaN material. A femtosecond laser is focused inside bulk GaN, several microns under the surface. The laser pulse energy is chosen such that in the focus area the laser breakdown threshold is exceeded and GaN is decomposed. The substrate is scanned by the laser beam until a continuous layer of decomposed material is formed under the surface.
© 2019 IEEE
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