Abstract
This article demonstrates for the first time to the best of our knowledge, the merits of InGaN/GaN multiple quantum wells (MQWs) grown on hollow n-GaN nanowires (NWs) as a plausible alternative for stable photoelectrochemical water splitting and efficient hydrogen generation. These hollow nanowires are achieved by a growth method rather not by conventional etching process. Therefore this approach becomes simplistic yet most effective. We believe relatively low Ga flux during the selective area growth (SAG) aids the hollow nanowire to grow. To compare the optoelectronic properties, simultaneously solid nanowires are also studied. In this present communication, we exhibit that lower thermal conductivity of hollow n-GaN NWs affects the material quality of InGaN/GaN MQWs by limiting In diffusion. As a result of this improvement in material quality and structural properties, photocurrent and photosensitivity are enhanced compared to the structures grown on solid n-GaN NWs. An incident photon-to-current efficiency (IPCE) of around ~33.3% is recorded at 365 nm wavelength for hollow NWs. We believe that multiple reflections of incident light inside the hollow n-GaN NWs assists in producing a larger amount of electron hole pairs in the active region. As a result the rate of hydrogen generation is also increased.
Highlights
Over the past two decades, III-V compound semiconductor materials have been used extensively in the field of optoelectronics
InGaN/GaN multiple quantum wells (MQWs) grown on hollow n-GaN NWs were unique structures and an incident photon-to-current efficiency (IPCE) as high as ~33.3% is being reported which is not the highest recorded number for nanostructures though it is the best reported IPEC value for a hollow NWs system without utilizing any external photocatalyst. n-GaN NWs, both solid and hollow, were grown on Si (111) substrates using plasma-assisted molecular beam epitaxy (PAMBE) but coaxial InGaN/GaN MQWs were grown on n-GaN NWs using metal organic chemical vapor deposition (MOCVD) process
The morphology of the n-GaN NWs was further revealed by high-resolution transmission electron microscopy (HR-TEM)
Summary
Over the past two decades, III-V compound semiconductor materials have been used extensively in the field of optoelectronics. Various GaN-based device structures with outstanding features have been developed and realized for their significant applications as light emitting diodes (LEDs), lasers, solar cells, and photodetectors[1,2] Besides these applications, metal-nitride semiconductors have emerged as a new generation of materials for the applications of photoelectrochemical (PEC) water splitting and hydrogen generation[3,4,5]. Zhao et al extensively studied the evolution of IPCE in various GaN devices[30] In this present scenario, to offer a polarization free larger effective area using m-plane InGaN/GaN heterostructures for maximum light harvesting and efficient hydrogen generation, a new growth method was applied to demonstrate a simpler but sophisticated InGaN/GaN heterostructure. InGaN/GaN MQWs grown on hollow n-GaN NWs were unique structures and an IPCE as high as ~33.3% is being reported which is not the highest recorded number for nanostructures though it is the best reported IPEC value for a hollow NWs system without utilizing any external photocatalyst. n-GaN NWs, both solid and hollow, were grown on Si (111) substrates using PAMBE but coaxial InGaN/GaN MQWs were grown on n-GaN NWs using metal organic chemical vapor deposition (MOCVD) process
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