Trap States and Carrier Diffusion in Czochralski (100) Single Crystal β-Ga2O3

Deep trap spectra and carrier diffusion lengths were measured for unintentionally doped β-Ga₂O₃ bulk crystals with (100) orientation. The 20-mm diameter, 15-mm length boule was pulled by the Czochralski method from gallium oxide in (010) direction. It is found that the net density of shallow donors in (100) plates cleaved from the crystal was 2.6 × 10¹⁷ cm⁻³, with ionization energies of 0.05 eV measured from admittance spectra. Three deep electron traps with respective ionization energies of 0.6 eV (concentration 1.1 × 10¹⁴ cm⁻³), 0.8 eV (concentration 3.9 × 10¹⁶ cm⁻³) and 1.1 eV (concentration 8.9 × 10¹⁵ cm⁻³) were detected by Deep Level Transient Spectroscopy. The dominant 0.8 eV trap is associated with the E2 centers due to Fe acceptors, the two other traps are the well documented E1 and E3 centers. The major deep acceptors in the lower half of the bandgap have optical ionization threshold of 2.3 eV and concentration of 4 × 10¹⁵ cm⁻³ and are believed to be due to the split Ga vacancies acceptors. The diffusion length of non-equilibrium charge carriers was 90 nm. The electrical properties of these (100) oriented crystals grown by Czochralski are quite similar to those synthesized by the undoped Edge-defined Film-Fed Growth technique.