Compensation in (2¯01) homoepitaxial β-Ga2O3 thin films grown by metalorganic vapor-phase epitaxy

Abstract

Homoepitaxial growth of β-Ga2O3 using metalorganic vapor-phase epitaxy (MOVPE) on several different crystal orientations has previously been studied, but growth on the (2¯01) plane has remained comparatively unexplored. To investigate this, we grew Si-doped and unintentionally doped (UID) homoepitaxial layers simultaneously on Sn-doped (2¯01) and (010) substrates under conditions optimized for (010) growth. We report herein on results from current–voltage and capacitance–voltage (IV and CV) and deep level transient spectroscopy (DLTS) characterization of Schottky diodes fabricated on these samples. Devices on (010) display nearly ideal Schottky diode JV and CV behaviors while for (2¯01) evidence of complete depletion of >2 μm thickness, UID epilayers are observed. The (2¯01) UID diodes exhibited Mott–Gurney space charge-limited transport and were completely depleted even at zero bias. Doping (2¯01) samples heavily with Si was sufficient to overcome background compensation and reproduce near-ideal diode behavior. DLTS data from these doped devices show, in addition to typical negative majority-carrier transients, positive transients with a broad energy distribution, possibly indicating traps on structural defects or surface states. An etch pit analysis under SEM revealed intricate structures of the grown layers. Cross-sectional TEM characterization of a (2¯01) sample revealed a high density of structural defects within the epitaxial layer, likely stacking faults. Hypotheses for the origins of the compensation in (2¯01) β-Ga2O3 homoepitaxial MOVPE growth under (010) growth conditions are discussed; the most likely explanation is the presence of defect states introduced by the stacking faults visible under TEM.