AlN/GaN Superlattice Channel HEMTs on Silicon Substrate

High-electron-mobility transistor (HEMT) with AlN/GaN superlattice (SL) channel has been demonstrated on a silicon substrate. High OFF-state breakdown voltage V
_BR
of 670 V (gate-drain spacing L
_GD
= 8 μm) along with a maximum output current of 196 mA/mm, a channel electron total mobility of 507 cm
²
/ V·s, and an ON/ OFF ratio of over 10
⁷
was achieved in this novel HEMT. For the HEMT with L
_GD
= 22 μm, a high V
_BR
of 1700 V was obtained with substrate floated. The influence of L
_GD
, the gate-source voltage V
_GS
, the isolated pattern, and substrate grounded and floated type was discussed to analyze the breakdown characteristics of HEMT. We investigated the trap states in the AlN/GaN SL channel of HEMTs by frequency-dependent capacitance and conductance measurements. A trap state density of 7.4×10
¹²
- 1.2×10
¹³
cm
^-2
eV
^-1
is located at E
_T
in a range of 0.29-0.33 eV of the main channel, while the trap state density in the parasitic channel decreases from 3.9×10
¹¹
cm
^-2
eV
^-1
at an energy of 0.27 eV to 1.1×10
¹¹
cm
^-2
eV
^-1
at an energy of 0.38 eV. The fabricated AlN/GaN SL channel HEMTs in this work reveal a great step toward the realization of the SL channel HEMTs on cost-effective silicon substrate and provide a novel technology for AlGaN multichannel devices to obtain high output current.