Heavily dopedn‐type InP and InGaAs epitaxial layers have been grown by metalorganic chemical vapor deposition at atmospheric pressure using tetraethyltin (TESn) as a dopant source. Sn‐doped InP and InGaAs layers have been grown with doping concentrations as high asn300K∼3.3×1019cm−3andn300 K∼6.1×1019cm−3, respectively. Hall measurements ofNd‐Naat 300 and 77 K indicate that the Sn is uncompensated up to these concentrations. Analysis of the Sn concentration in InP:Sn and InGaAs:Sn layers using secondary ion mass spectrometry, shows that all of the Sn is ionized in InP and InGaAs until a limit is reached that corresponds to the electrical limits. SIMS profiles also show that the use of TESn for the growthn+InP and InGaAs layers results in no severe memory effects and that abrupt Sn doping profiles can be achieved.