k-Space Associates, Inc.

k-Space Newsletter No. 42

published on 06/30/2020

Quantum Computing: k-Space Is Part of the Future with Low Temperature Qubit Fabrication

k‑Space recently installed a kSA BandiT non-contact optical temperature monitoring system on an AngstromEngineering (www.angstromengineering.com) Quantum Series Josephson junction fabrication platform designed for a large commercial partner.

The oxidation chamber utilizes the kSA BandiT system to monitor the substrate temperature in the room temperature to 250°C range. The non-contact measurement of temperatures in this regime is unique to k-Space by virtue of their patented band-edge-based temperature measurement technology.

k-Space engineered the kSA BandiT system to accommodate the fabrication system’s specific geometry and process materials. The oxide layer grown in this chamber is critical to the performance of the device and is largely influenced by the growth temperature. The ability to accurately measure the temperature of the wafer during oxidation creates a powerful level of control and should lead to a deeper understanding of this relationship.

Visit the full press release to learn more about this application and Angstrom Engineering’s platform.


Band-Edge Based Temperature Measurement Application Note

kSA BandiT utilizes the temperature dependence of a semiconductor’s inherent band gap to measure temperatures. With this technique, the sample either diffusely reflects or transmits light in the appropriate wavelength range. In the process, the sample can selectively absorb light with sufficient energy by transferring some of its energy to an electron in the valance band, causing it to be promoted to the conduction band. However, light that lacks the required energy can pass through the sample. The energy of the transition from absorbing to transmitting defines the optical absorption edge of the sample and is temperature dependent. kSA BandiT analyzes the spectrum of the diffusely reflected or transmitted light using a solid-state spectrometer to determine the wavelength of the absorption edge, which it converts to temperature via a set of material-specific calibration curves.

The figure above shows the kSA BandiT configuration in reflection mode, which is further explained in the application note. Read “kSA BandiT – Band Edge Based Temperature Measurement” to learn more.


kSA MOS Utilized in NREL’s World Record for Efficiency with Their Six-Junction Solar Cell

Photo Credit: “Scientists John Geisz (left) and Ryan France fabricated a solar cell that is nearly 50% efficient” by Dennis Schroeder, NREL 59970.

As most people in photovoltaics have heard, the National Renewable Energy Laboratory (NREL) set two exciting new world records for efficiency with their six-junction solar cell. The cell had a solar conversion efficiency of 47.1% under concentrated illumination, while another version of the cell had an efficiency of 39.2%, a record for one-sun illumination.

The device is quite complex, with a film stack of approximately 140 III-V based layers. Amazingly, the total device thickness is still narrower than a human hair. The technical paper, “Six-junction III-V solar cells with 47.1% conversion efficiency under 143 Suns concentration” by John Geisz, Ryan France, Kevin Schulte, Myles Steiner, Andrew Norman, Harvey Guthrey, Matthew Young, Tao Son, and Thomas Moriarty was published in Nature Energy (April 2020, Vol. 5) and gives further details on their accomplishment.

The kSA MOS was used for in situ curvature measurements during organometallic vapor phase epitaxy (OMVPE) growth of these devices. Congratulations to NREL on their remarkable accomplishment!


Easily Export Multiple Images with the Batch Export Feature

One feature that is popular among our k‑Space customers is the batch export feature. Check out this new video on our website that shows the batch export process for your images. This short video demonstrates the simple steps for downloading all of the images from a video at the same time. This is one of the many features we have added based on feedback from our customers on the type of functions they would like to see in our software. Visit the kSA 400 page to learn more about RHEED analysis capabilities.