Suboxide-mediated growth kinetics and etching in the metalorganic vapor phase epitaxy of GeO2

Rutile germanium dioxide (r-GeO2) is arising as a promising material in the field of ultra-wide bandgap semiconductors for power electronics applications. The deposition of high-quality r-GeO2 layers is crucial, but its growth kinetics is not trivial, especially when GeO desorption is involved. While this desorption can limit the growth rate of the material, it can also be exploited for in-situ etching procedures of potential technological interest. In this work we (i) suggest a plausible reaction pathway for GeO2 deposition in metalorganic vapor phase epitaxy (MOVPE) using isobutylgermane (iBuGe) and O2 precursors, (ii) describe the experimentally obtained temperature- and oxygen-flow-dependent growth rate by a simplified kinetic model that takes into account GeO desorption, and (iii) demonstrate the in-situ etching of deposited GeO2 layers in the absence of O2 inside the MOVPE reactor with an etch rate controlled by the iBuGe flow rate. The kinetic model confirms MOVPE of GeO2 to take place under a highly oxygen-rich flux stoichiometry, and predicts higher oxygen partial pressures, higher iBuGe partial pressures, or lower substrate temperatures (that still grant iBuGe decomposition) to increase the growth rate.