Emerging Applications of III‐Nitride Nanocrystals

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154944/1/pssa201900885_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154944/2/pssa201900885.pd

Group III-nitride nanowire structures for photocatalytic hydrogen evolution under visible light irradiation

The performance of photochemical water splitting over the emerging nanostructured photocatalysts is often constrained by their surface electronic properties, which can lead to imbalance in redox reactions, reduced efficiency, and poor stability. We have investigated the impact of surface charge properties on the photocatalytic activity of InGaN nanowires. By optimizing the surface charge properties through controlled p-type dopant (Mg) incorporation, we have demonstrated an apparent quantum efficiency of ∼17.1% and ∼12.3% for InGaN nanowire arrays under visible light irradiation (400 nm–490 nm) in aqueous methanol and in the overall neutral-pH water splitting reaction, respectively

Micrometer-thick, atomically random SiGeSn for silicon-integrated infrared optoelectronics

A true monolithic infrared photonics platform is within the reach if strain and bandgap energy can be independently engineered in SiGeSn semiconductors. However, this Si-compatible family of group-IV semiconductors is typically strained and inherently metastable, making the epitaxial growth fraught with extended defects and compositional gradients. Herein, we control the growth kinetics to achieve epitaxial Si0.06Ge0.90Sn0.04 layers lattice-matched to a Ge on Si substrate, with a uniform content and a thickness up to 1.5 {\mu}m. Atomic-level studies demonstrate high crystalline quality and uniform composition and confirm the absence of short-range ordering and clusters. Room temperature spectroscopic ellipsometry and transmission measurements show direct bandgap absorption at 0.83 eV and a reduced indirect bandgap absorption at lower energies. Si0.06Ge0.90Sn0.04 photoconductive devices exhibit a dark current similar to that of Ge devices and a slightly higher room-temperature spectral responsivity reaching 1 A/W above 0.82 eV (i.e. below 1.5 {\mu}m wavelengths). These results underline the enhanced performance in lattice-matched devices and pave the way to introduce SiGeSn semiconductors as building blocks to implement the long-sought-after silicon-integrated infrared optoelectronics

Photoelectrochemical reduction of carbon dioxide using Ge doped GaN nanowire photoanodes

We report on the direct conversion of carbon dioxide (CO₂) in a photoelectrochemical cell consisting of germanium doped gallium nitride nanowire anode and copper (Cu) cathode. Various products including methane (CH₄), carbon monoxide (CO), and formic acid (HCOOH) were observed under light illumination. A Faradaic efficiency of ∼10% was measured for HCOOH. Furthermore, this photoelectrochemical system showed enhanced stability for 6 h CO₂ reduction reaction on low cost, large area Si substrates