Carrier transport in LPCVD grown Ge-doped β-Ga2O3/4H-SiC isotype heterojunction

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.