Effect of In-Situ Silicon Carbon Nitride (SiCN) Cap Layer on Performances of AlGaN/GaN MISHFETs

AlGaN/GaN metal insulator semiconductor heterostructure field effect transistors (MISHFETs) with different thickness of
in-situ
silicon carbon nitride (SiCN) cap layer were investigated. It was found that
in-situ
SiCN layer not only increases the two dimensional electron gas (2DEG) density, but also effectively passivates the surface of the AlGaN/GaN MISHFET. The fabricated device with 2 nm-thick SiCN cap layer exhibits superior device performances, such as larger maximum transconductance (
$\text{g}_{\mathrm{ m}}$
) and higher on/off drain-current ratio (
$\text{I}_{\mathrm{ ON}}/{\mathrm{ I}}_{\mathrm{ OFF}}$
) compared to those of the device without SiCN cap layer.