P-type β-gallium oxide: A new perspective for power and optoelectronic devices

• Published in: Materials today physics 2017-12, Vol.3, p.118-126
• Main Authors: Chikoidze, Ekaterine, Fellous, Adel, Perez-Tomas, Amador, Sauthier, Guillaume, Tchelidze, Tamar, Ton-That, Cuong, Huynh, Tung Thanh, Phillips, Matthew, Russell, Stephen, Jennings, Mike, Berini, Bruno, Jomard, Francois, Dumont, Yves
• Format: Article
• Language: English
• Subjects: Beta-Ga2O3; Electrical properties; Hole conductivity; Thermodynamic calculations; Wide band gap semiconductor
• ISSN: 2542-5293; 2542-5293
• DOI: 10.1016/j.mtphys.2017.10.002

Wide-bandgap semiconductors (WBG) are expected to be applied to solid-state lighting and power devices, supporting a future energy-saving society. Here we present evidence of p-type conduction in the undoped WBG β-Ga2O3. Hole conduction, established by Hall and Seebeck measurements, is consistent with findings from photoemission and cathodoluminescence spectroscopies. The ionization energy of the acceptor level was measured to be 1.1eV above the valence band edge. The gallium vacancy was identified as a possible acceptor candidate based on thermodynamic equilibrium Ga2O3 (crystal) – O2 (gas) system calculations (Kroger theory) which revealed a window without oxygen vacancy compensation. The possibility of fabricating large diameter wafers of β-Ga2O3 of p and n type nature, provides new avenues for high power and deep UV-optoelectronic devices. Photograph of a commercial, 2-inch β-Ga2O3/c-sapphire epiwafer from Nanovation; Evidence of p type Ga2O3: Temperature dependence of the Hall hole concentration, ln(p) versus 1000/T plot leading to a carrier activation energy Ea = 0.56 ± 0.05 eV. Valence band photoemission spectra for the reference Si-doped β -Ga2O3/β -Ga2O3 (n-type) and our β - Ga2O3/c-sapphire (p-type). [Display omitted] •Evidence of p-type conduction in the undoped wide band gap β-Ga2O3.•The ionization energy of the acceptor level was measured to be 1.1eV above the valence band edge.•p and n type Ga2O3, opens perspective for power and deep UV-optoelectronic devices.