High Current and Linearity AlGaN/GaN/-Graded-AlGaN:Si-doped/GaN Heterostructure for Low Voltage Power Amplifier Application

In this letter, the AlGaN/GaN/graded-AlGaN:Si-doped/GaN double channel (GDC-SI) high electronic mobility transistors (HEMTs) with high saturation current density and linearity have been reported for low voltage applications. Compared with the standard AlGaN/GaN/AlGaN/GaN double channel GaN (SDC) HEMTs, the GDC-SI HEMTs exhibited the higher saturation current, the broader and flatter transconductance profile, the lower transconductance ( ${g}_{\text {m}}{)}$ derivatives, and lower on-resistance ( ${R}_{\text {on}}{)}$ . Due to the Si-doped graded bottom barrier present in GDC-SI HEMTs, the profile of current gain cutoff frequency ( ${f}_{\text {T}}{)}$ and the maximum oscillation frequency ( ${f}_{\text {max}}{)}$ were flatter with the bias voltage increased. The output power density of 0.75 W/mm and power added efficiency (PAE) of 58% were achieved for GDC-SI HEMTs, at the drain voltage of 7 V and the test frequency of 3.6GHz. The output third-order intercept point (OIP3) of 39.3 dBm and saturation current density of 1909 mA/mm are achieved, which are the state-of-the-art saturation current and OIP3 in the double-channel GaN HEMTs.