High Linearity AlGaN/GaN/Graded AlGaN/GaN Double Channel HEMTs for High/Low Voltage Applications

In this article, the AlGaN/GaN/graded-AlGaN/GaN (DCGC) and the AlGaN/GaN/Si-doped graded-AlGaN/GaN (Si-doped DCGC) HEMTs are reported for high linearity. The graded channel can slow down the descent of transconductance (
$g_{\mathrm{m}}$
). The flatter
$g_{\mathrm{m}}$
can be achieved by the double-channel devices with a lower graded channel. The current gain cut-off frequency (
$f_{\mathrm{T}}$
) and the maximum oscillation frequency (
$f_{\max}$
) decline slowly as the bias voltage increases. Due to the above 200V breakdown voltage and the lower leakage current, the DCGC HEMTs can be used for high-voltage and high-efficiency applications. The 65% of power added efficiency (PAE) and 11.4 W/mm of output power density are achieved by the DCGC HEMTs, at 3.6 GHz, 60V of the
$V_{\mathrm{d}}$
. The Si-doped DCGC HEMTs are more suitable for low-voltage applications, because of the high saturation output current density and lower knee voltage. The 39.3 dBm of output third-order intercept point (OIP3) and 10.2 dB of OIP3/
$P_{\text{DC}}$
are realized by Si-doped DCGC HEMTs. The OIP3 is higher than that of the GaN HEMTs.