Unlocking the full potential of SSRM for GaAs: Nanoscale carrier profiling in nano-ridge laser diodes

Owing to its direct bandgap and high electron mobility, gallium arsenide (GaAs) plays a key role in the development of high-performance electronic and optoelectronic devices. Accordingly, the accurate characterization of two-dimensional carrier distributions is essential to support their integration. Scanning spreading resistance microscopy (SSRM) is a well-established method for quantitative carrier profiling in silicon, while its application to III-V semiconductors is complicated by the non-ohmic nature of the tip-sample contact. Therefore, we present a systematic study of SSRM on GaAs, focusing on the optimization of both electrical (bias) and mechanical (force and repeated scanning) measurement conditions. Key performance metrics, including dynamic range, doping sensitivity, and repeatability, are evaluated to assess measurement reliability. Building on these insights, we demonstrate the applicability of SSRM to advanced nanoscale devices through a case study supporting the growth optimization of monolithically integrated GaAs nano-ridge laser diodes on silicon. The complex geometry and facet-dependent growth in these structures lead to non-trivial active dopant distributions, making them an ideal platform to highlight the capabilities of SSRM. Finally, we extend the use of SSRM to failure analysis by leveraging the reverse tip sample (RTS) methodology for site-specific electrical characterization of electrical stress-induced localized degradation defects in aged GaAs-on-Si laser diodes. In summary, this work establishes SSRM as a powerful technique for quantitative two-dimensional carrier profiling in both n- and p-type GaAs and demonstrates its value for the development, optimization, and failure analysis of advanced GaAs-based devices.