High‐quality modulation doped In0.53Ga0.47As/InP heterostructures have been grown by atmospheric pressure metalorganic chemical‐vapor deposition (MOCVD) using solid trimethylindium source. The two‐dimensional nature of electrons bound in the In0.53Ga0.47As/InP heterojunctions is proved by a Shubnikov‐de Haas effect experiment. Electron Hall mobilities as high as 12000, 83000, 98000, and 92000 cm2/V s at 300, 77, 40, and 4.2 K are obtained, respectively. The electron effective mass is measured to bem@B|CR=0.043m0by cyclotron resonance experiments on the samples with two‐dimensional electron sheet concentrations of (3.0–3.7)×1011/cm2. From far‐infrared impurity absorption data the ionization energy of the residual donors in the MOCVD‐grown In0.53Ga0.47As is determined to be 2.95 meV.