Evaluation and Mitigation of Impurities in Additively Manufactured Epitaxial Gallium Nitride

Gallium nitride (GaN) that is additively manufactured from a liquid gallium precursor allows for the possibility of manufacturing high-performance semiconducting materials with complex device geometries. However, mitigation of impurities such as carbon and oxygen in the final GaN film is crucial to manufacturing functional films with these methods. In this work, two methods of mitigating native gallium oxide in the liquid gallium precursor were employed and evaluated: (1) "wet" etching of the precursor in solution before GaN growth and (2) "dry" etching of the precursor during the growth using a reducing carrier gas. The carbon impurity content of films grown by using this method was also studied. Data obtained via scanning electron microscopy, time-of-flight secondary ion mass spectrometry, and hot probe electrical characterization indicated that both etch methods were linked to a significant reduction in oxygen content in the resulting GaN film. Photoluminescence data further indicated that the gas-phase reactive additive manufacturing process is linked to a reduction in luminescent defects in the resulting film as compared to commercial GaN grown via chemical vapor deposition.