Peculiarities of electrochemical capacitance-voltage profiling of GaP-based p-i-n structures

Abstract

Gallium phosphide is a crucial A³B⁵ semiconductor for integrated photonics and optoelectronics due to its wide bandgap, high radiation resistance, nonlinear optical properties, and the possibility of integration with silicon technology. To ensure the reproducibility of the device parameters, it is necessary to control the distribution of free charge carrier concentration in multilayer epitaxial structures based on GaP. This paper studies the capabilities of electrochemical capacitance-voltage profiling method for the diagnostics of GaP-based p-i-n-structures with sharp interfaces. A comparative analysis of three types of electrolytes – aqueous solutions of NH₄F, H₂SO₄ and HCl – was carried out. Their influence on the etching behavior, the accuracy of depth determination, and the reliability of the obtained majority charge carrier concentration profiles was investigated. It was demonstrated that the use of NH₄F and HCl leads to nonuniform local etching, while H₂SO₄ provides the polishing character of etching but fails to overcome the insoluble interface between the i- and n-regions. An approach involving the sequential use of H₂SO₄ and HCl during the etching of this region was developed. The approach was successfully tested and enabled the acquisition of reliable concentration profiles across the depth of the studied p-i-n GaP structures.