« Previously: 'Wetting transparency' grows defect-free electronics  
To prove that the newly grown materials were as fit as the bulk substrate to design electronic devices, a group of researchers at MIT grew AlGaInP–GaInP double heterojunction light-emitting diodes (LEDs) on a graphene-overlaid GaAs substrate.

The LEDs not only exhibited I–V curves and turn-on voltages (1.3V) comparable to those of LEDs directly grown on a bare GaAs substrate, their electroluminescence spectra also exhibited nearly identical performance, according to the study.

The LEDs were then exfoliated from the GaAs substrate (leveraging the graphene layer as a non-stick interface from which the active layers could be peeled-off) and transferred to a Si substrate without noticeable performance degradation. The layers being peeled-off are only a few micrometres thick and the graphene-coated wafer remains untouched, ready for re-use without ever being sacrificed in the end-device. That means enormous cost savings, especially so when having to rely on non-silicon substrates.

MIT_graphene_02 (cr) Figure 1: Cross-sectional SEM image of AlGaInP–GaInP double heterojunction LEDs on a graphene–GaAs substrate LEDs (left), and (right) the I–V curves of these MIT logo-shaped LEDs (emitting red light). At the bottom right, the electroluminescence spectra of the LEDs grown on graphene–GaAs substrates and directly on GaAs.

"Since the epilayers grown by remote homoepitaxy can be released from the graphene surface, this 2D material-based layer transfer (2DLT) technique offers the potential to grow, transfer and stack any electronic and photonic materials on 2D materials without the lattice matching limitation. This will open a pathway towards defect-free hetero-integration of dissimilar materials while saving the cost of expensive and exotic substrates," the paper stated.

MIT_graphene_03 (cr) Figure 2: Diagram showing the different steps of the graphene-based layer transfer technique applied to LEDs.

« Previously: 'Wetting transparency' grows defect-free electronics