We report on the magneto-transport properties of InAs/AlGaSb open quantum dot structures. The open dot structures have been fabricated by using electron beam lithography. The open dot structures are characterized by magnetoresistance measurements at 4.2 K. In addition to the Shubnikov-de Hass oscillations, aperiodic magnetoresistance fluctuations have been observed at low magnetic fields below 1 T. The amplitude of the fluctuations was quite large even at 4.2 K in comparison with the case of the GaAs/AlGaAs system. Electron-wave interference effect and phase-breaking times in InAs mesoscopic structures are discussed from the analyses using correlation functions of magneto-conductance fluctuations.