The development of GaN-on-diamond devices offers bright prospects for the creation of high-power density electronics. This article presents a process of fabricating GaN-on-diamond structure by depositing diamond films on dual sides, including heat dissipation diamond film and sacrificial carrier diamond film. Prior to heat dissipation diamond film layer preparation, aluminum nitride (AlN) is chosen as a dielectric layer and pretreated by nanodiamond (ND) particles, to enhance the nucleation density. Zeta potential measurements and X-ray photoelectron spectroscopy are used to analyze the AlN surface after each treatment. The results show that oxygen-terminated ND particles tend to adhere to an AlN surface because the oxygen-terminated NDs have –COOH and –OH groups, and hold a negative potential. On the contrary, fluorine-terminated AlN prefers to attract the hydrogen-terminated ND seeds, which resulted in higher diamond nucleation density. Based on this preliminary study, a dense high-quality GaN-on-diamond wafer is successfully produced by using AlN as the dielectric layer and a diamond film as the sacrificial carrier.

The increasing demand for portable and low-power electronics for applications in self-powered devices and sensors has spurred interest in the development of efficient piezoelectric materials, via which mechanical energy from ambient vibrations can be transformed into electrical energy for autonomous devices, or which can be used in strain-sensitive applications. Semiconducting piezoelectric materials are ideal candidates in the emerging field of piezotronics and piezophototronics, where the development of a piezopotential in response to stress/strain can be used to tune the band structure of the semiconductor and hence its electronic and/or optical properties. Furthermore, research into nanowires of these materials has intensified due to the enhancement of piezoelectric properties at the nanoscale. In this regard, nanowires of ZnO and the III-nitrides have been extensively studied, but the piezoelectric properties of non-nitride III–V semiconductor nanowires remain less-explored. Indeed, direct measurements of the piezoelectric properties of single III–V nanowires are tellingly rare due to the difficulties associated with measurements of piezoelectric properties of nanoscale objects using conventional scanning probe microscopy techniques. This review addresses the challenges related to the study of piezoelectricity in III–V nanowires and the opportunities that lie therein in terms of device applications.

The spectrally and temporally resolved luminescence of three-dimensional (3D) InGaN/GaN microrods and planar light emitting diode (LED) structures is studied for different energy densities of fs-laser excitation pulses and for different sample temperatures. We find an energy density threshold above which irreversible modifications of the structures take place, which leads to a decrease of the luminescence intensity and a change in the intensity ratio of the GaN to the InGaN luminescence. Due to the quantum confined Stark effect, a biexponential decay characteristic is found in the planar structure, while the 3D microrods with nonpolar InGaN quantum wells on their sidewalls show a monoexponential decay of the InGaN luminescence. For both structures, the decay of the luminescence becomes faster with increasing energy density per pulse. However, the luminescence of the planar LED decays faster with increasing temperature, while the opposite trend is found for the 3D sample.

This paper reviews our recent investigations of compound semiconductors and heterovalent interfaces using the technique of aberration-corrected scanning transmission electron microscopy. Bright-field imaging of compound semiconductors with a collection angle that is comparable in size to the incident-beam convergence angle is demonstrated to provide better atomic-column visibility for lighter elements in comparison with the more traditional high-angle annular-dark-field approach. Several pairs of Group II–VI/Group III–V compound semiconductors with zincblende structure have been studied in detail. These combinations are all valence-mismatched (i.e., heterovalent), and include CdTe/InSb (Δa/a ≤ 0.05%), ZnTe/InP (Δa/a = 3.8%), and ZnTe/GaAs (Δa/a = 7.4%). CdTe/InSb (001) interfaces are observed to be defect-free with a slight lattice contraction at the interface plane. For interfaces with larger lattice-parameter mismatch, the primary interfacial defects are identified as Lomer edge dislocations and perfect 60° dislocations. However, the atomic structure of the dislocation cores has not yet been unambiguously determined.

Metamorphic epitaxy offers the possibility of growing devices on wafers composed of different materials that might be larger than the native bulk substrates for a potential cost-reduction of III–V components; this is especially important when native substrates with desired lattice constants are not available. This article reviews the concepts of metamorphic epitaxy of III–V compound semiconductor materials and examines how they have been applied to the development of advanced transistor devices. These metamorphic devices are expected to be a key enabler of future heterogeneous integrated circuits in which Si and III–V devices are monolithically integrated on a wafer scale using complementary metal oxide semiconductor-like process flows.

The epitaxial integration of III–V optoelectronic devices on silicon will be the enabling technology for full-scale deployment of silicon photonics and the key to improving communication systems. Silicon photonics also offer new opportunities for the realization of ultracompact and fully integrated sensing systems operating in the mid-infrared (MIR) regime of the spectrum. In this article, we review recent developments, through several approaches, in the direct metamorphic epitaxial growth of various III–V materials-based lasers on silicon substrates. We show that GaAs-based 1.3-μm III–V quantum dot lasers and GaSb-based MIR quantum-well lasers grown on silicon substrates can operate with low threshold current density and high operating temperature, which hold promise for the future.

In this work, we present a detailed investigation of the growth of palladium-seeded GaAs nanowires. Nanowires grown on GaAs (111)B substrates consist of three different morphologies, denoted as curly (containing multiple kinks), inclined (relative to the substrate, such as 〈001〉), and vertical. We show that the relative yield of the different types is controllable by a combination of V/III ratio and temperature, where vertical and inclined nanowires are promoted by a high temperature and low V/III ratio. These growth conditions are expected to promote a higher Ga incorporation into the Pd particle, which is confirmed by energy dispersive x-ray analysis. We propose that the observed relationship between particle composition and nanowire morphology may be related to the particle phase, with liquid particles promoting straight nanowire growth. In addition, particles at the tips of nanowires are sometimes observed to be smaller than the initial particle size, suggesting that Pd has been lost during the growth process. Finally, we demonstrate the importance of initial particle size-control to interpret diameter changes after growth.

Chemical wet etching on c-plane sapphire wafers by three etching solutions (H3PO4, H2SO4, and H3PO4/H2SO4 mixing solution) was studied. Among these etching agents, the mixing H3PO4/H2SO4 solution has the fastest etching rate (1.5 μm/min). Interestingly, we found that H2SO4 does not etch the c-plane sapphire wafer in thickness; instead, a facet pyramidal pattern is formed on the c-plane sapphire wafer. GaN light-emitting diode (LED) epitaxial structure was grown on the sapphire wafer with the pyramidal pattern and the standard flat sapphire wafer. X-ray diffraction and photoluminescence measurement show that the pyramidal pattern on the sapphire wafer improved crystalline quality but augmented the compressive stress level in the GaN LED epilayer. The horizontal LED chips fabricated on the pyramidal-patterned sapphire wafer have a larger light output than the horizontal LED chips fabricated on the standard flat sapphire wafer by 20%.

Semiconductor nanowires (NWs) are characterized by an extraordinarily large surface-to-volume ratio. Consequently, surface effects are expected to play a much larger role than in thin films. Here, we review a research focused on the impact of the surface on the electrical and optical properties of catalyst-free GaN NWs with growth direction <0001>. Using a combination of complementary experimental techniques, it has been shown that the Fermi level is pinned at the NW sidewall surfaces, resulting in internal electric fields and in full depletion for NWs below a critical diameter. Deoxidation of the surfaces unpins the Fermi level, leading to enhanced radiative recombination of excitons. Prominent absorption below the bandgap is caused by the Franz-Keldysh effect. Close to the surface, the ionization energy of donors is reduced. The consideration of surface-induced effects is mandatory for an understanding of the physical properties of NWs as well as their application in devices.