Homoepitaxial Growth and the Electronic Structure of Degenerately Si Doped <i>β</i> ‐Ga ₂ O ₃ (100) Oriented Thin Films

Abstract In this work, homoepitaxial growth and in‐depth study on the electronic structure of Si doped β‐Ga 2 O 3 thin films on (100) oriented Fe doped Ga 2 O 3 substrates are reported. Carrier concentrations ranging from 3.7 × 10 18 cm −3 to 1.6 × 10 20 cm −3 were achieved with Si doping level from 0.01% to 1%. The highest conductivity achieved is 468.8 S/cm, making the films promising ohmic contact electrodes. Synchrotron based hard x‐ray photoemission spectroscopy (HAXPES) were used to gain insights into the evolution of electronic structure of the degenerately doped films. The results show that the optical bandgaps of the films increase with Si doping, because of the progressive occupation of the bottom of the conduction band by the electrons, i.e., Burstein‐Moss shift (∆BM). On the other hand, doping induced bandgap renormalization (∆BGR) leads to narrowing of the fundamental bandgap. The ∆BGR value is slightly higher than those of (010) oriented films at a similar carrier concentration. The anisotropic nature of β‐Ga 2 O 3 , including the crystal field splitting and the dielectric constant, was found to contribute to the observed crystal orientation‐dependent ∆BGR behavior. By understanding the Burstein‐Moss and bandgap renormalization effects, the electronic and optical properties of β‐Ga 2 O 3 materials can be optimized for optoelectronic device applications.