# Dirac fermion reflector by ballistic graphene sawtooth-shaped npn junctions

## TL;DR

This paper demonstrates a graphene-based Dirac fermion reflector using sawtooth-shaped npn junctions, enabling control over ballistic carrier trajectories and reflection, which is promising for high-mobility graphene transistors.

## Contribution

It introduces a novel sawtooth-shaped npn junction design that effectively reflects Dirac fermions in graphene, advancing Dirac fermion optics applications.

## Key findings

- Resistance enhancement observed in np+n regime
- Good agreement with numerical simulations
- Potential for ultrahigh-mobility graphene transistors

## Abstract

We have realized a Dirac fermion reflector in graphene by controlling the ballistic carrier trajectory in a sawtooth-shaped npn junction. When the carrier density in the inner p-region is much larger than that in the outer n-regions, the first straight np interface works as a collimator and the collimated ballistic carriers can be totally reflected at the second zigzag pn interface. We observed clear resistance enhancement around the np+n regime, which is in good agreement with the numerical simulation. The tunable reflectance of ballistic carriers could be an elementary and important step for realizing ultrahigh-mobility graphene field effect transistors utilizing Dirac fermion optics in the near future.

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Source: https://tomesphere.com/paper/1702.04039