Info
Info
News Article

Enhancing Performance Of III-V Nanowires

Using InGaAs on InAs stems grown on graphene could benefit solar cell and laser technology
Imagine a field of small wires-standing at attention like a tiny field of wheat-gathering the Sun’s rays as the first step in solar energy conversion.


Researchers at the University of Illinois at Urbana-Champaign have achieved new levels of performance for seed-free and substrate-free arrays of nanowires from class of materials called III-V directly on graphene.


These compound semiconductors hold particular promise for applications involving light, such as solar cells or lasers.





A dense array of nanowires grown directly on graphene. The insets show a higher magnification SEM view of the array and a STEM image of a single, axially heterostructured InGaAs/InAs nanowire


“Over the past two decades, research in the field of semiconductor nanowires has helped to reshape our understanding of atomic-scale crystal assembly and uncover novel physical phenomena at the nanometre scale," explains Xiuling Li, a professor of electrical and computer engineering at Illinois. 


In the March 20th issue of Advanced Materials, the researchers present the first report of a novel solar cell architecture based on dense arrays of coaxial p-n junction InGaAs nanowires on InAs stems grown directly on graphene without any metal catalysts or lithographic patterning.


“In this work, we have overcome the surprising structure (phase segregation) and successfully grown single phase InGaAs and demonstrated very promising solar cell performance," explains postdoctoral researcher Parsian Mohseni, first author of the study. 





The InGaAs/InAs nanowire array can be lifted from its graphene base and transferred to alternative platforms for bendable device applications (Credit : Parsian Mohseni)


“Depending on the materials, nanowires can be used for functional electronics and optoelectronics applications," Mohseni adds.  “The main benefits of this III-V photovoltaic solar cell design are that it is fairly low-cost, substrate-free, and has a built-in back side contact, while being conducive to integration within other flexible device platforms."


Li’s research group uses a method called van der Waals epitaxy to grow nanowires from the bottom up on a two-dimensional sheet, in this case, graphene.  Gases containing gallium, indium, and arsenic are pumped into a chamber where the graphene sheet sits, prompting the nanowires self-assemble, growing by themselves into a dense carpet of vertical wires across the graphene’s surface.


In their earlier work in Nano Letters 2013 using a graphene sheet, the researchers discovered that InGaAs wires grown on graphene spontaneously segregate into an InAs core with an InGaAs shell around the outside of the wire.


To improve the materials’ efficiencies for solar power conversion, the researchers bypassed the unique Van der Waals epitaxy induced spontaneous phase segregation by inserting InAs segments in between.


The resulted ternary InGaAs NW arrays are vertical, non-tapered, controllable in size, height, and doping, and broadly tunable in composition thus energy for monolithic heterogeneous integration with 2D Van der Waals sheets including graphene.





Schematic representations of the three different nanowire geometries investigated (a-c) and a diagram of a nanowire array-on-graphene prototype solar cell device structure (d). The characteristic illuminated current density-voltage (J-V) curves and external quantum efficiency (EQE) spectra obtained from the three distinct device structures are shown in the bottom left and bottom right, respectively  (Credit : Parsian Mohseni)


Under air mass 1.5 global solar illumination, the core-shell In0.25Ga0.75As (Eg ~ 1.1 eV) nanowire arrays on graphene demonstrate a conversion efficiency of 2.51  percent, representing a new record for substrate-free, III-V NW-based solar cells.


“Although InGaAs is far from being the optimum bandgap materials for high efficiency solar cells, the direct epitaxy on graphene platform established here has significant implications for a wide variety of III-V compound semiconductor NW based solar cells on graphene, as well as light emitters and multi-junction tandem solar cells, all of which can be released for flexible applications," Li says.


This article has been adapted from one by Rick Kubetz, Engineering Communications Office, University of Illinois at Urbana-Champaign.


 




AngelTech Live III: Join us on 12 April 2021!

AngelTech Live III will be broadcast on 12 April 2021, 10am BST, rebroadcast on 14 April (10am CTT) and 16 April (10am PST) and will feature online versions of the market-leading physical events: CS International and PIC International PLUS a brand new Silicon Semiconductor International Track!

Thanks to the great diversity of the semiconductor industry, we are always chasing new markets and developing a range of exciting technologies.

2021 is no different. Over the last few months interest in deep-UV LEDs has rocketed, due to its capability to disinfect and sanitise areas and combat Covid-19. We shall consider a roadmap for this device, along with technologies for boosting its output.

We shall also look at microLEDs, a display with many wonderful attributes, identifying processes for handling the mass transfer of tiny emitters that hold the key to commercialisation of this technology.

We shall also discuss electrification of transportation, underpinned by wide bandgap power electronics and supported by blue lasers that are ideal for processing copper.

Additional areas we will cover include the development of GaN ICs, to improve the reach of power electronics; the great strides that have been made with gallium oxide; and a look at new materials, such as cubic GaN and AlScN.

Having attracted 1500 delegates over the last 2 online summits, the 3rd event promises to be even bigger and better – with 3 interactive sessions over 1 day and will once again prove to be a key event across the semiconductor and photonic integrated circuits calendar.

So make sure you sign up today and discover the latest cutting edge developments across the compound semiconductor and integrated photonics value chain.

REGISTER FOR FREE

VIEW SESSIONS

Info
×
Search the news archive

To close this popup you can press escape or click the close icon.
×
Logo
×
Register - Step 1

You may choose to subscribe to the Compound Semiconductor Magazine, the Compound Semiconductor Newsletter, or both. You may also request additional information if required, before submitting your application.


Please subscribe me to:

 

You chose the industry type of "Other"

Please enter the industry that you work in:
Please enter the industry that you work in:
 
X
Info
X
Info
{taasPodcastNotification}
Live Event