Probing charge transport and background doping in MOCVD grown (010) $\beta$-Ga${}_2$O${}_3$

Abstract

A new record-high room temperature electron Hall mobility (${\mu }_{RT}=194c{m}^2/Vs$ at $n\sim 8\times 10^{15}c{m}^{-3}$) for $\beta$-Ga2O3 is demonstrated in the unintentionally doped thin film grown on (010) semi-insulating substrate via metalorganic chemical vapor deposition (MOCVD). A peak electron mobility of $\sim 9500c{m}^2/Vs$ is achieved at 45 K. Further investigation on the transport properties indicate the existence of sheet charges near the epi-layer/substrate interface. Si is identified as the primary contributor to the background carrier in both the epi-layer and the interface, originated from both surface contamination as well as growth environment. Pre-growth hydrofluoric acid cleaning of the substrate lead to an obvious decrease of Si impurity both at interface and in epi-layer. In addition, the effect of MOCVD growth condition, particularly the chamber pressure, on the Si impurity incorporation is studied. A positive correlation between the background charge concentration and the MOCVD growth pressure is confirmed. It is noteworthy that in a $\beta$-Ga2O3 film with very low bulk charge concentration, even a reduced sheet charge density can play an important role in the charge transport properties.

19 pages, 5 figures