High Threshold Voltage Uniformity and Low Hysteresis Recessed-Gate Al2O3/AlN/GaN MISFET by Selective Area Growth

In this paper, a normally off Al
₂
O
₃
/AlN/GaN MISFET on Si substrate for achieving high threshold voltage stability and uniformity is obtained based on selective area growth. A thin AlN space layer (SL, ~1 nm) is adopted to GaN-based template, and the AlGaN/GaN heterostructure is selectively grown on the template to naturally form a recessed structure. By insertion of the AlN SL, the Al
₂
O
₃
/AlN/GaN interface trapping and scattering effects are effectively suppressed. As a result, a low threshold voltage hysteresis (Δ V
_th
, 80 mV at maximum gate sweep voltage of 10 V by dc I-V measurement and smaller than 200 mV in linear region by pulse I-V measurement) and a high peak field-effect mobility (μ
_FE
) of 192 cm
²
/V·s are obtained in Al
₂
O
₃
/AlN/GaN MISFET. It is a significant improvement compared with Al
₂
O
₃
/GaN MISFET without AlN SL. The Al
₂
O
₃
/AlN/GaN MISFET also exhibits a maximum drain current (I
_d,max
) of 620 mA/mm, a low on-resistance (R
_ds
,
_ON
) of 9.6 Ω·mm, and a high uniformity of V
_th
(2.5 ± 0.1 V).