Sub-surface Imaging of Porous GaN Distributed Bragg Reflectors via Backscattered Electrons.

In this article, porous GaN distributed Bragg reflectors (DBRs) were fabricated by epitaxy of undoped/doped multilayers followed by electrochemical etching. We present backscattered electron scanning electron microscopy (BSE-SEM) for sub-surface plan-view imaging, enabling efficient, non-destructive pore morphology characterization. In mesoporous GaN DBRs, BSE-SEM images the same branching pores and Voronoi-like domains as scanning transmission electron microscopy.

Carrier dynamics at trench defects in InGaN/GaN quantum wells revealed by time-resolved cathodoluminescence.

Time-resolved cathodoluminescence offers new possibilities for the study of semiconductor nanostructures - including defects. The versatile combination of time, spatial, and spectral resolution of the technique can provide new insights into the physics of carrier recombination at the nanoscale. Here, we used power-dependent cathodoluminescence and temperature-dependent time-resolved cathodoluminescence to study the carrier dynamics at trench defects in InGaN quantum wells - a defect commonly found in III-nitride structures.

Crystalline Interlayers for Reducing the Effective Thermal Boundary Resistance in GaN-on-Diamond.

Integrating diamond with GaN high electron mobility transistors (HEMTs) improves thermal management, ultimately increasing the reliability and performance of high-power high-frequency radio frequency amplifiers. Conventionally, an amorphous interlayer is used before growing polycrystalline diamond onto GaN in these devices. This layer contributes significantly to the effective thermal boundary resistance (TBR) between the GaN HEMT and the diamond, reducing the benefit of the diamond heat spreader.

Integrated Wafer Scale Growth of Single Crystal Metal Films and High Quality Graphene.

We report on an approach to bring together single crystal metal catalyst preparation and graphene growth in a combined process flow using a standard cold-wall chemical vapor deposition (CVD) reactor. We employ a sandwich arrangement between a commercial polycrystalline Cu foil and c-plane sapphire wafer and show that close-spaced vacuum sublimation across the confined gap can result in an epitaxial, single-crystal Cu(111) film at high growth rate. The arrangement is scalable (we demonstrate 2″ wafer scale) and suppresses reactor contamination with Cu.

A Peeling Approach for Integrated Manufacturing of Large Monolayer h-BN Crystals.

Hexagonal boron nitride (h-BN) is the only known material aside from graphite with a structure composed of simple, stable, noncorrugated atomically thin layers. While historically used as a lubricant in powder form, h-BN layers have become particularly attractive as an ultimately thin insulator, barrier, or encapsulant. Practically all emerging electronic and photonic device concepts currently rely on h-BN exfoliated from small bulk crystallites, which limits device dimensions and process scalability.

Characterisation of InGaN by Photoconductive Atomic Force Microscopy.

Nanoscale structure has a large effect on the optoelectronic properties of InGaN, a material vital for energy saving technologies such as light emitting diodes. Photoconductive atomic force microscopy (PC-AFM) provides a new way to investigate this effect. In this study, PC-AFM was used to characterise four thick (∼130 nm) In x Ga 1 - x N films with = 5%, 9%, 12%, and 15%.

Dislocations in AlGaN: Core Structure, Atom Segregation, and Optical Properties.

We conducted a comprehensive investigation of dislocations in AlGaN. Using aberration-corrected scanning transmission electron microscopy and energy dispersive X-ray spectroscopy, the atomic structure and atom distribution at the dislocation core have been examined. We report that the core configuration of dislocations in AlGaN is consistent with that of other materials in the III-Nitride system.