One of the challenges for the nanoscale device fabrication of III-V semiconductors is controllable postdeposition doping techniques to create ultrashallow junctions. Here, we demonstrate nanoscale, sulfur doping of InAs planar substrates with high dopant areal dose and uniformity by using a self-limiting monolayer doping approach. From transmission electron microscopy and secondary ion mass spectrometry, a dopant profile abruptness of ϳ3.5 nm/decade is observed without significant defect density. The n + / p + junctions fabricated by using this doping scheme exhibit negative differential resistance characteristics, further demonstrating the utility of this approach for device fabrication with high electrically active sulfur concentrations of ϳ8 ϫ 10 18 cm −3 .

Scanning spreading resistance microscopy (SSRM) is a promising new tool for dopant profiling in semiconductor materials. We present the results of a SSRM study of the cross section of a metalorganic chemical vapor deposited grown optoelectronic structure. The SSRM measurements are compared with the secondary ion mass spectrometry (SIMS) and excellent spatial agreement is obtained. However, we find that obtaining quantitative agreement with SIMS is complicated by the differing nonlinear I-V characteristics of n- and p-type InP. The results suggest that obtaining quantitative agreement with SIMS would require calibration of each SSRM probe tip with both n- and p-type materials. The high spatial resolution of the technique is demonstrated by our ability to easily resolve the 17.5 nm quantum well and barrier layer structure of the device. The results suggest that the greatest strength of SSRM will be the delineation of complex buried semiconductor structures.

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