Abstract
We investigate cyclotron emission (CE) of graphene by a graphene/GaAs-AlGaAs heterostructure hybrid device. To date, this challenging subject - CE of graphene- has not been successfully observed. We employ chemical vapor deposited graphene on top of GaAs-AlGaAs heterostructure with two dimensional electron gas (2DEG) 105 nm beneath the surface. To generate CE, we apply perpendicular magnetic field to the device up to 1 T, giving rise Landau level energy spacing E gr between n = 0 to n = 1 of graphene about 37 meV. While the applied source-drain bias on graphene larger than E gr/2e, nonequilibrium carriers would be generated, and CE occurs at the hot-spot corners or even within the bulk regime. To detect CE, we consider Egr actually is matched to the phonon energy (LO and TO phonons) of GaAs crystal. By absorbing CE, 2DEG in GaAs layer will be heated up and we expect this kind bolometric effect can be measured by the change of the longitudinal resistance of 2DEG. The device is cooled down in a cryostat with varying temperature from 1.4 K to 110 K and magnetic field up to 8 T. Electrical contacts were made separately to contact Graphene and 2DEG. Clear magnetophonon resonances of 2DEG are observed at 80 K, supporting the role of LO phonon in magnetoresistance. We adopt two different device designs and use two different modulation ways to catch CE signals. We do not find a clear signal of CE in graphene, although the noise level seemly becomes larger in the target conditions. The absence of CE may suggest that radiation signal is much weaker than one expected or the magnetoresistance of 2DEG is not sensitive enough for the present experiment. For future works, we suggest to improve the quality of graphene and to adopt more sensitive detective mechanism.