Conduction, dielectric and interface properties of Al_2O_3 films on GaAs deposited by the e-beam evaporation technique

摘要

We report the results of resistivity, conduction mechanism, dielectric and interface properties of 750 and 1500 A thick Al_2O_3 films deposited by the e-beam evaporation technique for surface passivation of GaAs-based devices. The typical near-zero bias leakage currents were varying from 85 fA to 6 pA corresponding to a resistivity variation of 3.6 × 10~(11) to 8.8 × 10~(11) Ω cm for 750 A films. Similarly for 1500 A films, the corresponding currents were varying from 85 fA to 3 pA indicating a resistivity variation of 1.5 × 10~(11) to 6.6 × 10~(12) Ω cm. The 750 A films showed typically almost constant current densities of under 5 × 10~(-8) A cm~(-2) compared to varying (1.2-7.5) × 10~(-8) A cm~(-2) for 1500 A films. These observations were further corroborated by conduction mechanism results. Although the 750 A films showed trends of Frenkel-Poole (FP) conduction for medium electric field strengths with lesser variation, the 1500 A films also showed FP conduction but with more variation and scatter in data. Additionally, we report the results for the estimates of dynamic dielectric constant estimated from the FP conduction dominated region. The average value for 750 A films was 2.17 compared to 4.43 for 1500 A films. The static dielectric constant, interface properties were measured by the capacitance-voltage (CV) technique. The results indicate that a stable interface is possible by using the e-beam evaporation technique contrary to reports available in the literature. The range of values (including the data of both the films) obtained for dielectric constant, fixed charge density and fast interface state density were 3.6-4.6, (0.7-1.4) × 10~(12) cm~(-2) and (0.5-1) × 10~(13) cm~(-2) eV~(-1) respectively for these films.