III–V semiconductors such as InP and GaAs are direct bandgap semiconductors with significantly higher absorption compared to silicon. The high absorption allows for the fabrication of thin/ultra-thin solar cells, which in turn permits for the realization of lightweight, flexible, and highly efficient solar cells that can be used in many applications where rigidity and weight are an issue, such as electric vehicles, the internet of things, space technologies, remote lighting, portable electronics, etc. However, their cost is significantly higher than silicon solar cells, making them restrictive for widespread applications. Nonetheless, they remain pivotal for the continuous development of photovoltaics. Therefore, there has been a continuous worldwide effort to reduce the cost of III–V solar cells substantially. This topical review summarises current research efforts in III–V growth and device fabrication to overcome the cost barriers of III–V solar cells. We start the review with a cost analysis of the current state-of-art III–V solar cells followed by a subsequent discussion on low-cost growth techniques, substrate reuse, and emerging device technologies. We conclude the review emphasizing that to substantially reduce the cost-related challenges of III–V photovoltaics, low-cost growth technologies need to be combined synergistically with new substrate reuse techniques and innovative device designs.

In the near future, technological advances driven by the Fourth Industrial Revolution will boost the demand for integrated, power-efficient miniature lasers, which are important for optical data communications and advanced sensing applications. Although top-down fabricated III–V semiconductor micro-disk and micro-ring lasers have been shown to be efficient light sources, challenges such as etching-induced sidewall roughness and poor fabrication scalability have been limiting the potential for high-density on-chip integration. Here, we demonstrate InP micro-ring lasers fabricated with a highly scalable epitaxial growth technique. With an optimized cavity design, the optically pumped micro-ring lasers show efficient room-temperature lasing with a lasing threshold of around 50 μJ cm–2 per pulse. Remarkably, through comprehensive modeling of the micro-ring laser, we demonstrate lasing mode engineering experimentally by tuning the vertical ring height. Our work is a major step toward realizing the high-density monolithic integration of III–V miniature lasers on submicrometer-scale optoelectronic devices.

InAs nanowires have been considered as good candidates for infrared photodetection. However, one-dimensional geometry of a nanowire makes it unsuitable for broadband light absorption. In this work, we propose and design InAs nanosheet arrays to achieve polarization-independent, angle-insensitive, and ultrawide infrared absorption. Simulations demonstrate that two-dimensional InAs nanosheets can support multiple resonance modes, thus leading to a strong and broadband absorption from visible light to mid-wave infrared. Moreover, we can tune polarization-dependent property in InAs nanosheets to be polarization-insensitive by forming a nanosheet based clover-like and snowflake-like nanostructures. We further optimized the design of InAs nanosheet arrays based on such structures and achieved high absorption (up to 99.6%) covering a broad wavelength range from 500 to 3200 nm. These absorption properties are much superior to their nanowire and planar film counterparts, making it attractive for infrared photodetection applications. The architecture of such nanostructures can provide a promising route for the development of high-performance room-temperature broadband infrared photodetectors.

There is a strong demand for III–V nanostructures of different geometries and in the form of interconnected networks for quantum science applications. This can be achieved by selective area epitaxy (SAE) but the understanding of crystal growth in these complicated geometries is still insufficient to engineer the desired shape. Here, the shape evolution and crystal structure of InP nanostructures grown by SAE on InP substrates of different orientations are investigated and a unified understanding to explain these observations is established. A strong correlation between growth direction and crystal phase is revealed. Wurtzite (WZ) and zinc‐blende (ZB) phases form along <111>A and <111>B directions, respectively, while crystal phase remains the same along other low‐index directions. The polarity induced crystal structure difference is explained by thermodynamic difference between the WZ and ZB phase nuclei on different planes. Growth from the openings is essentially determined by pattern confinement and minimization of the total surface energy, regardless of substrate orientations. A novel type‐II WZ/ZB nanomembrane homojunction array is obtained by tailoring growth directions through alignment of the openings along certain crystallographic orientations. The understanding in this work lays the foundation for the design and fabrication of advanced III–V semiconductor devices based on complex geometrical nanostructures.

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