Understanding C and H impurities in doping of (Al,Ga)2O3

Schematic of the changes in defect levels vs composition for Si, C, and H dopants in β-(Al,Ga)2O3. We include the (+/–) electronic transitions of C and Si substitutional, interstitial Hi and substitutional HO dopants. The energies are shown relative to the conduction band edge of (Al,Ga)2O3 alloys (shaded yellow region).
Schematic of the changes in defect levels vs composition for Si, C, and H dopants in β-(Al,Ga)2O3. We include the (+/–) electronic transitions of C and Si substitutional, interstitial Hi and substitutional HO dopants. The energies are shown relative to the conduction band edge of (Al,Ga)2O3 alloys (shaded yellow region).

CMI researchers at Lawrence Livermore National Laboratory conducted the research for this highlight

Achievement

  • Incorporated carbon and hydrogen impurities in metal organic vapor deposition methods used to grow high quality epitaxial films of ultrawide band gap semiconductor Ga2O3 and wider-band gap (Al,Ga)2O3 alloys. 
  • Identified that incorporating these impurities can complicate the realization of highly n-type material for certain growth conditions and Al contents.

Significance and Impact

  • Confirmed that Si donors act as effective shallow donors for Al contents <70%.
  • Revealed that C and H dopants can act as soluble compensators in even modest Al-content (Al,Ga)2O3 alloys.
  • Identified composition regimes and process conditions that will be problematic for achieving highly conductive (Al,Ga)2O3 alloys.

Hub Goal Addressed

  • Increase the speed of discovery and integration.
  • Develop predictive models for real materials.

S. Mu, M. Wang, J. B. Varley, J. L. Lyons, D. Wickramaratne, C. G. Van de Walle, Role of carbon and hydrogen in limiting n-type doping of monoclinic (AlxGa1−x)2O3. Phys Rev B. 105, 155201 (2022).