Metal-insulator-semiconductor Tunneling Microscope: Two-dimensional Dopant Profiling of Semiconductors with Conducting Atomic-force Microscopy

We have demonstrated quantitative carrier profile analysis of InP and Silicon using the newly invented Metal-Insulator-Semiconductor Tunneling Microscope (MISTM). The MISTM operates by measuring the current between a conducting Atomic Force Microscope (AFM) probe tip and an oxidized semiconductor sample. Scanning Current-Voltage measurements using the MISTM on an InP staircase sample showed a different behavior for n- and p-types and changed with dopant concentration. This behavior is believed to be dominated by the tunneling through a Schottky type contact, which is influenced by surface states and the intervening thin oxide layer. A quantitative model that includes the properties of the tip, the oxide, and the surface and bulk properties of InP was used to explain the experimental results. The excellent agreement between the data and the model suggest that MISTM can be used as a tool for quantitative two dimensional carrier profiling in InP and other semiconductor materials in the future.