Enhanced Breakdown Voltage With High Johnson's Figure-of-Merit in 0.3-$\mu{\rm m}$ T-gate AlGaN/GaN HEMTs on Silicon by $({\rm NH}_{4})_{2}{\rm S}_{x}$ Treatment

Enhanced OFF -state breakdown voltage has been observed in ammonium sulfide [(NH
₄
)
₂
S
_x
]-treated AlGaN/GaN high electron mobility transistors (HEMTs) on Si substrate without compromising the unit gain cutoff frequencies. About six times higher OFF -state breakdown voltage (BV
_gd
) and three orders of magnitude higher I
_ON
/I
_OFF
ratio were observed in the (NH
₄
)
₂
S
_x
-treated 0.3- μm T-gate conventional AlGaN/GaN HEMTs on Si substrate. In addition, three orders of magnitude lower surface leakage current (~3.0 μA/mm to ~3 nA/mm) have also been observed on the (NH
₄
)
₂
S
_x
-treated devices. The calculated Johnson's figures of merit (J-FOM = BV
_gd
× f
_T
) is 5.41 × 10
¹²
V/s, which is the highest value reported so far for 0.3- μm T-gate conventional SiN passivated AlGaN/GaN HEMTs without the incorporation of field plate. No significant drain current collapse was observed on the (NH
₄
)
₂
S
_x
-treated devices.