The selective epitaxy of GaAs was demonstrated in the metalorganic vapor phase epitaxy of GaAs utilizing diethylgallium chloride [Ga(C2H5)2Cl] and AsH3. No GaAs will deposit on SiO2, Si3N4, or SiONxunder normal growth conditions, i.e., 600–800 °C at 0.1 atm reactor pressure. Unlike other forms of selective epitaxy, there is no enhanced growth rate at the edge of the selectively grown regions. The selectivity is a result of the reduced adsorption of the growth precursor, probably GaCl, on the masking material relative to the exposed GaAs areas. Similar selectivity should be possible for Al and In containing semiconductors using an analogous growth chemistry.