Gallium-oxide trench-type devices

摘要

Gallium oxide (β-Ga_2O_3) is a suitable material for next generation high power devices because of its huge critical electricfield strength. However, most current device structures are not enough to take advantage of the full potential of Ga_2O_3because these structures are optimized for material properties of silicon. To bring out the potential of Ga_2O_3, we proposea trench structure. First, we made Ga_2O_3 metal-oxide-semiconductor Schottky barrier diodes (MOSSBDs). The HfO_2film was deposited on the trench bottom and sidewall. Ga_2O_3 MOSSBD had a small leakage current level, and had abouta 40% lower forward voltage than that of the commercially available SiC SBDs. We thus successfully demonstrated thatthe performance of Ga_2O_3 devices can exceed that of SiC devices. Next, we made Ga_2O_3 junction barrier Schottky (JBS)diodes. p-type region was made by p-type NiO. The Ga_2O_3 JBS diode had several orders of magnitude smaller leakagecurrent than that of the normal SBD. This result indicates that the electric field at the Schottky junction decreased as aresult of using the JBS structure. Finally, we fabricated Ga_2O_3 trench MOS field effect transistors. We used a staticinduction transistor-type structure that can be made only with n-type semiconductors. Si-doped Ga_2O_3 n~+ contact and ndriftlayers were grown on Sn~- doped (001) Ga_2O_3 substrate with HVPE. The gate dielectric was HfO_2. The deviceshowed clear current modulation characteristics and a maximum current density of 1.36 kA/cm~2. The device had a highon-off ratio of over 10~7.