Carrier transport in LPCVD grown Ge-doped <i>β</i>-Ga2O3/4H-SiC isotype heterojunction
Taha Saquib, Fatih Akyol, Hamdin Ozden, Nalla Somaiah, J. C. Sahoo, R. Muralidharan, Digbijoy N. Nath
Abstract
We report on the study of electron transport and band offset across β-Ga2O3/4H-SiC N–n isotype heterojunction. N-type β-Ga2O3 of thickness 2.7 μm was grown using low-pressure chemical vapor deposition using germanium (Ge) as the dopant on an n-type 4H-SiC substrate. The grown epilayer having (−201) orientation was verified through XRD. Temperature-dependent I–V and C–V measurements were performed (50–300 K) to investigate the transport properties across the heterojunction. First, lateral diodes were fabricated on β-Ga2O3, and from C–V, n-doping was estimated to be 2.3×1017cm−3 in the epilayer while the Schottky barrier height was estimated to be 1.75 eV. In top-down I–V sweeps, the reverse current across the heterojunction exhibited marginal dependence on temperature, indicating a possible tunnelling-based transport mechanism, while the forward current exhibited an exponential dependence on both temperature and the applied bias. The band diagram indicated the formation of a two-dimensional electron gas (2DEG) at the hetero-interface, which was indirectly confirmed using C–V measurement and TCAD simulation at low temperatures. From the position of the Fermi level in SiC and band diagram, a conduction band offset of 0.4–0.5 eV was estimated between β-Ga2O3 and 4H-SiC.