A method for locally controlling an electrical potential of a semiconductor structure or device, and thus locally controlling lateral and/or vertical photoelectrochemical (PEC) etch rates.
PEC etching uses above-bandgap illumination to generate carriers (specifically holes) needed to etch III-nitrides. The electrochemical potential of the semiconductor material surface relative to the electrolyte causes holes to be drawn toward the semiconductor-electrolyte interface in n-type (unintentionally-doped or doped) material, allowing them to participate in the electrochemical reactions necessary for material removal. Because the etching mechanism relies heavily on the absorption of incident light and the electrochemical potential of the semiconductor material relative to the electrolyte, PEC etching can be defect-selective, dopant-selective, and bandgap-selective. Most applications of PEC etching have pertained to vertical etching of the material, either through direct illumination of the material surface, or by illumination through a masking layer. However, specific descriptions of local control of the etch process through modifications of the electrochemical component of etching have not been presented.
Researchers at the University of California, Santa Barbara have developed a scheme for fabricating III-nitride semiconductor structures wherein a highly selective photo-induced etch is achieved through strategic modification of the local electrochemical potential of the semiconductor structure relative to the electrolyte. This is accomplished with:
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PEC etching, indPEC, indssl