MOCVD Synthesis and In Situ Processing of Gallium Oxide Based Heterostructures

Over the past 10 years, β-Ga₂O₃ with an ultra-wide bandgap of 4.8 eV has emerged as a promising material for next generation power electronics. In this talk, I will outline our work on metal-organic chemical vapor deposition (MOCVD) synthesis, processing, and characterization of β-Ga₂O₃ epitaxial thin films and heterostructures for next generation power devices.
In the first half of the talk, I will describe our work on MOCVD synthesis of β-(Al_xGa_1-x)₂O₃/Ga₂O₃ based modulation-doped heterostructures using triethylaluminum (TEAl) and triethylgallium (TEGa) as precursors for Al and Ga, respectively. TEAl and TEGa undergo pyrolysis at low substrate temperatures via β-hydrogen elimination mitigating carbon contamination in the epilayers. This enabled us to synthesize β-(Al_xGa_1-x)₂O₃/Ga₂O₃ heterostructures at low substrate temperatures, key for forming sharp interfaces, abrupt doping profiles and minimal carbon contamination. Electrical characterization of these two-dimensional electron gas (2DEG) revealed record high room temperature electron mobility of 187 cm²/Vs, the highest to-date for MOCVD grown β-(Al_xGa_1-x)₂O₃/Ga₂O₃ 2DEGs. Moreover, at cryogenic temperatures, some of these 2DEGs display Shubnikov-de Haas oscillations.
In the second half of the talk, I will outline our work on in situ etching of gallium oxide using tert-butyl chloride (TBCl) in an MOCVD reactor. In situ etching followed by regrowth opens up the possibility of forming contact layers for gallium oxide based electronic devices where the critical contact layer-to-channel interface is not exposed to atmospheric contamination. This will be key for both pushing the performance envelope of gallium oxide based radio frequency and power devices. I will discuss the etch mechanism of gallium oxide using TBCl and electrical characterization of in situetched and regrown ohmic contacts.