Vertical Conduction of AlGaN‐on‐SiC Diodes with Buffer‐Layer‐Free Heterointerfaces

Fully vertical AlGaN power diodes are fabricated on conductive SiC substrates using a hetero‐epitaxial growth technique via metal–organic chemical vapor deposition. To minimize parasitic resistance in vertical conduction, the growth of high‐Al‐composition buffer layer shall be omitted, which increases the potential barrier at the heterointerface. In this experiment, an epitaxial AlGaN layer with uniform Al content is grown directly on 4H‐SiC (0001) substrates. Crack‐free AlGaN layer with flat surface is successfully obtained for Al composition of x = 0.3. Cross‐sectional transmission electron microscopy and electron energy‐loss spectroscopy reveal an abrupt heterointerface without any peculiar compositional modulation. Fully vertical Schottky‐barrier diodes are fabricated on 0.5 μm‐thick AlGaN drift layers. The forward current density–voltage (J–V) characteristics for the diodes exhibit excellent rectification characteristics with an on/off ratio of >10 9 and differential resistance R diff (=dV/dJ) less than 1 mΩcm 2 at V F = 4 V. These results suggest that this method is promising for realizing fully vertical power devices using AlGaN material.