A new approach to the study of semiconductor growth mechanisms is described which utilizes surface science and related photon‐based techniques. It is possible to study growth processes over the pressure range 5×10−11to 103mbar through the use of an isolatable atmospheric pressure reactor described briefly. As an illustration of the potential of the surface science approach, the effectiveness of the reducing hydrogen atmosphere employed in the pregrowth bake of a GaAs (100) metal‐organic vapor phase epitaxy (MOVPE) substrate in removing surface carbon and oxygen is determined using Auger electron spectroscopy. It is shown that at a pressure of 0.5 mbar of H2, temperatures as low as 600 K are sufficient to remove the surface carbon and oxygen contamination present on the substrate following wet chemical etching and heating in ultrahigh vacuum. This result implies that the conventional MOVPE sample bake at high temperatures (>850 K), in H2and AsH3is not necessary to produce clean substrates. Following the H2treatment the GaAs(100) surface gives rise to a (1×1) low‐energy electron diffraction pattern suggesting that it has been stabilized towards reconstruction via hydrogen chemisorption.