Metastable Changes in the Dark Conductivity of Undoped and Carbon‐Doped β‐Ga₂O₃

Measurements of the electrical dark conductivity σ D of undoped and carbon‐doped β‐Ga 2 O 3 thin films reveal a metastable increase upon illumination with sub‐bandgap light. In the relaxed state, σ D shows activated behavior for T > 250 K with an activation energy of 0.68 and 0.63 eV for undoped and C‐doped β‐Ga 2 O 3 , respectively. For T < 250 K, σ D approaches a constant value of ≈6 × 10 −12 Ω −1 cm −1 . Illumination with sub‐bandgap light results in an increase of the dark conductivity by up to 6 orders of magnitude. This state is metastable and relaxes with time. The data indicate the presence of a broad distribution of localized states in the bandgap. The time and temperature dependence of the relaxation is investigated for doped and undoped samples. The data can be described by a sum of two and three stretched exponential decays for undoped and carbon‐doped β‐Ga 2 O 3 , respectively. From the time constants of the decays, the energetic depth of the localized defect states is estimated.