Characteristics of InAs/GaSb Line-Tunneling FETs With Buried Drain Technique

The combination of the InAs/GaSb heterojunction and the line-tunneling mechanism is considered as one of the most promising approaches to simultaneously obtain high ON-state current (
${I}_{ \mathrm{\scriptscriptstyle ON}}$
) and low subthreshold swing (SS) in tunneling field effect transistors (TFETs). However, in an InAs/GaSb line-tunneling field effect transistor (LTFET), the isolation between the source and the drain is a big issue. The leakage current path could lead to complete loss of the OFF-state characteristics in extreme cases. The “cantilever” or “airbridge” structure is usually introduced to cutoff the leakage path. However, it also induces serious reliability problems and brings additional process complexity. In this article, an N+ doped buried drain is first proposed to form a reverse biased p-n junction with the
$\text{P}\boldsymbol +$
source and effectively cuts the leakage current path off. The InAs
$\boldsymbol /$
GaSb LTFETs with this buried drain technique exhibits
${I}_{ \mathrm{\scriptscriptstyle ON}} \boldsymbol / {I}_{ \mathrm{\scriptscriptstyle OFF}} > {10}^{{7}}$
and SS < 60 mV
$\boldsymbol /$
dec for five decades of current. Besides the excellent performance, the buried drain technique keeps the device planar and brings no additional fabrication complexity, which is of great significance for future experimental investigation and the low power applications.