Researchers Demonstrate Record-High Molecular Beam Epitaxy Growth Rates

Achievement date: 
2015
Outcome/accomplishment: 

Georgia Institute of Technology researchers affiliated with the NSF-funded Engineering Research Center (ERC) for Quantum Energy and Sustainable Solar Technologies (QESST), which is headquartered at Arizona State University, demonstrated record-high growth rates for molecular beam epitaxy (MBE). This major accomplishment was recognized in 2015 at the oldest-running U.S. semiconductor conference (WOCSEMMAD), where QESST’s Brendan Gunning received the “most valuable contribution” award (see top figure). 

Impact/benefits: 

The high growth rate demonstrated by the researchers will enable growth of thick indium gallium nitride (InGaN) layers required for high-efficiency nitride-based solar cells. This improvement in growth technology will have great impact on commercialization of low-cost nitride solar cells.

Explanation/Background: 

Although InGaN alloys are promising candidates for full-solar-spectrum photovoltaic applications, these alloys exhibit major challenges, such as growing thick, high-quality InGaN layers. Major maintenance has been performed on the Georgia Tech MBE system, with a new nitrogen plasma source and two additional cryogenic pumps that allow for higher growth rates while still maintaining a high-purity growth environment.

By varying both the RF power and the N2 flow, researchers at Georgia Tech have been able to achieve growth rates ranging from 950 nm/hr to ~8 μm/hr with excellent uniformity over a 2” wafer. Illustrative growth rates are depicted in the accompanying graph.