Alumnus Prakash Palamedu Sundaram wins best paper award at CS MANTECH

Alumnus Prakash Palamedu Sundaram is the recipient of the best student paper award at the 2023 International Conference on Compound Semiconductor Manufacturing Technology (CS MANTECH) for his paper titled, "Fabrication and Analysis of β-Ga2O3 Schottky Diodes with Drift Layer Grown by MOCVD on (001)." The paper offers a detailed examination of Schottky Barrier Diodes (SBDs) fabricated on two different Si-doped homoepitaxial beta-gallium oxide (β-Ga2O3) thin films grown using the metal organic chemical vapor deposition method. The research presented is the outcome of collaborative work done by teams led by Professors Steven Koester (ECE) and Bharat Jalan (CEMS) and Agnitron Technology based in Chanhassen, Minnesota. Besides lead author Sundaram, the other authors were Fengdeng Liu, Fikadu Alema, Andrei Osinsky, Bharat Jalan, and Steven J. Koester.

Conference chair David Meyer (United States Naval Research Laboratory) acknowledged Sundaram’s work by saying: "Your significant contribution to the field exemplifies excellence and innovation. We are delighted to recognize your outstanding work."

Fifty percent of the world’s electricity is controlled by semiconductor power devices which are integral to all power electronic systems. With electronics becoming increasingly prevalent in consumer, industrial, medical, and transportation sectors, these power devices play a crucial role in the economy by influencing the cost and efficiency of these systems. Since the transition from vacuum tubes to solid-state devices in the 1950s, semiconductor power devices have been dominated by silicon. However, silicon-based electronics face significant inefficiencies in high-power applications due to silicon's small bandgap (approximately 1.1 eV) and a low breakdown electric field of about 0.3 MV/cm. These properties entail thicker material layers for high-voltage devices, which leads to increased resistance and conduction losses. Besides, silicon-based power electronics tend to be bulkier and generate more heat.

Wide bandgap technologies have emerged as promising alternatives due to their potential for enhanced efficiency across various applications. For example, in wind turbines, wide bandgap materials could theoretically boost operational efficiency from 45 percent to 85 percent. Other potential applications include variable frequency drives for electric motors, traction inverters, DC boost inverters, and on-board battery chargers for electric vehicles.

Among wide bandgap materials, silicon carbide (SiC) and gallium nitride (GaN), with bandgaps of 3.2 eV and 3.4 eV respectively, have undergone significant development over recent decades. However, these materials are nearing their theoretical performance limits, and there are significant barriers to their widespread adoption because of the high costs associated with their production. 

Over the past decade, β-Ga2O3 has gained significant attention as a promising ultrawide bandgap (UWBG) semiconductor material for next-generation power electronics applications. Its large bandgap (approximately 4.9 eV), high critical breakdown field of about 8 MV/cm, and substantially large Baliga’s figure of merit which is 4 to 10 times greater than that of GaN and SiC make it particularly attractive. The availability of affordable native single-crystal substrates made from cost-effective melt-grown techniques and the ability to grow high-quality epitaxial films with controllable doping further enhance its appeal for high-power vertical devices.

A critical step towards bringing β-Ga2O3 devices to the market is to grow a robust, high-quality epitaxial layer on large wafers. The metal organic chemical vapor deposition (MOCVD) technique is a well-established method for the commercial growth of thin films. However, despite the advantages offered by the combination of (001) plane of orientation and the MOCVD technique, the growth of high-quality MOCVD films on (001) β-Ga2O3 for use in Schottky barrier diodes (SBDs) had not yet been reported.

In a first of its kind, the team conducted a systematic study of the Schottky barrier diodes fabricated on two different Si-doped homoepitaxial β-Ga2O3 thin films with (001) and (010) orientation using the MOCVD method. The team’s demonstration marks a significant step towards commercializing β-Ga2O3 devices. It could pave the way for the development of more efficient, high-power electronic systems that could have a substantial positive impact on various industries and everyday technologies.

CS MANTECH formally recognized the authors of the best student paper from the 2023 conference at its 2024 conference that concluded in May in Tucson, Arizona. The honor comes with a cash prize for the principal student author.

Prakash Sundaram graduated with his doctoral degree in spring 2024. He completed his dissertation under the guidance of ECE faculty Steven Koester who is the Russell J. Penrose Professor in Nanotechnology. Sundaram’s dissertation is titled, “Advancing Beta-Gallium Oxide Schottky Diodes for Next Generation Power Electronics Applications.” It focuses on harnessing the potential of β-Ga2O3, an ultra-wide bandgap material for next-generation high-power electronic devices, despite challenges such as the absence of p-type doping and limitations imposed by its flat valence band dispersion. Sundaram recently joined Intel as a module development engineer.