Ga₂O₃-based electronic and optoelectronic devices can be affected by the presence of defects with deep energy levels in the gap. Therefore, several studies of deep-level defects in Ga₂O₃-based materials and devices using different experimental and modelling techniques have been reported [1]. However, a comprehensive understanding of deep-level defects in Ga₂O₃ is still missing. An effective method to obtain the properties of electrically active defects in Ga₂O₃ is deep-level transient spectroscopy (DLTS) in conjunction with high-resolution Laplace-DLTS (L-DLTS) [2]. 

In this work, conventional DLTS and high-resolution L-DLTS have been used to characterise deep-level traps in (010) β-Ga₂O₃ epilayers grown by metal organic vapour deposition on native Sn-doped substrates. The ~2 µm thick epilayers were either doped with silicon to ~1.5x10¹⁷ cm^-3 or unintentionally doped (UID) during growth, resulting in an electron concentration of ~10¹⁶ cm^-3. The electrical measurements were carried out on Au Schottky barrier diodes. In the Si-doped samples only one electron trap with an emission activation energy of 0.42 eV (E_0.42 or E9 according to trap labelling in Ref. [1]) and a concentration of (6-8)x10¹³ cm^-3 has been detected. In the UID samples, in addition to E9, two other traps with activation energies for electron emission of 0.10 eV (E_0.10 or E10) and 0.53 eV (E_0.53 or E1) have been observed. Dependencies of electron emission rate (e_n) on the electric field (E) as well as the concentration-depth profiles {N_T(W)} have been measured and analysed for E10 and E9. The e_n(E) dependence for E10 is characteristic for a donor energy level, while that for E9 indicates an acceptor level. The N_T(W) dependencies show non-uniform spatial distributions of both E10 and E9 in the UID epilayer, with the concentration of E10 dropping from about 1x10¹⁵ cm^-3 at 1.5 µm from the surface to about 2x10¹³ cm^-3 at 0.5 µm. The N_T(W) dependencies indicate potential out-diffusion of atoms from the Sn-doped substrate into the epilayer as a likely source of the appearance of E10 and E9. The results obtained are compared with those available in the literature and possible origins of the detected traps are discussed.

 

[1] Wang, Z., Chen, X., Ren, F.-F., Gu, S. & Ye, J. Deep-level defects in gallium oxide. J. Phys. D: Appl. Phys. 54, 043002 (2021).

[2] Peaker, A. R., Markevich, V. P. & Coutinho, J. Tutorial: Junction spectroscopy techniques and deep-level defects in semiconductors. J. Appl. Phys. 123, 161559 (2018).