CCA Simulation Approach for the Fabrication of Micro Spoke Structures by Wet Etching Process on GaN Substrate

GaN, as a representative of single-crystal group III nitride semiconductors, has excellent properties suitable for processing high-power devices, and anisotropic wet etching allows the preparation of complex and precise microstructures on GaN. In this paper, we propose a simulation method based on continuous cellular automata (CCA) to simulate the etching fabrication process of spoke structures on GaN (0 0 0 1) crystallographic plane. The metamerism rate in the CCA simulation is based on the removal rate of different types of atomic groups, which can be obtained from the step flow rate model established in the GaN <0001> crystallographic zone. The interfacial evolution is based on a step-flow mechanism, with the removal of metastable cells based on the change of metastable cell occupation values. The etching process of four spoke structures spaced at 10° from the (1 0 -1 0) crystallographic plane to the (1 1 -2 0) crystallographic plane is simulated under H 3 PO 4 (85%wt) solution conditions at 140°C. Comparing the results after simulated etching with experiments, the tip retraction length and the sidewall shortening distance show small errors, indicating the validity of the CCA simulation.