Entrance Effects In A Horizontal Atmospheric-Pressure MOCVD Reactor

The flow pattern of process gas at atmospheric pressure in a rectangular cross-section, horizontal MOCVD reactor was determined by pyrolyzing trimethylindium to produce an indium "smoke." Growth tubes with 9cm and 30cm entrance lengths and various internal geometries were tested. Entrance effects dominated the flow behavior for all tubes tested. This behavior is not generally recognized but is predicted from entrance-length theory. Use of a gas diffuser positioned slightly upstream from the susceptor produced no visible backflow of pyrolyzed reagent while greatly improving uniformity of flow over the susceptor. Im-proved control over GaAs film growth was obtained using a diffuser. These results lead to an improved design for a horizontal MOCVD reactor growth tube.