ゲルマニウム／ひずみーシリコンヘテロ接合を用いたトンネル電界効果トランジスタ

1. 背向偏置效应：在较宽的中间ID区域内，尽管Ioff增加，但离子显著增加，SS显著降低。负VB是由于隧道电流受到抑制，导致SSmin降低。结果表明，从锗源到硅沟道后界面可产生隧道电流，特别是垂直隧道电流，电流可通过硅沟道后界面附近形成的反转层。由于隧穿效率高，垂直隧穿电流比横向隧穿电流表现出更高的漏极，这些垂直隧穿的电子在sSi沟道的ge源下方和近后界面处形成n源。然而，sSi通道主要由VG控制，因为正极绝缘子的EOT比BOX薄得多。因此，这种正VB诱导的垂直隧道效应对提高Ge/sSi TFET的性能具有很大的前景，并且可以有效地利用VB与VG同步应用于Fin FET、纳米线等多栅极结构中来提高TFET的性能。实验证实，改进后的漏极掺杂浓度为1018 cm-3，适合进一步提高性能。在本研究中，通过将栅极介电材料Al2O3改为HfO2， EOT从2.5 nm缩放到1.5 nm。结果表明，越薄的EOT器件具有越高的电流。然而，由于Ge和Si的大Dit， hfo2器件的泄漏电流增加。

1. Back biasing effectPositive VB yields a significant increase in Ion and decrease in SS in a wide range of middle ID region in spite of the increase in Ioff. Negative VB is attributable to the suppressed tunneling current, resulting in lower SSmin. It is revealed that tunneling current, especially vertical tunneling can occur from Ge-source to back interface of sSi-channel and current can flow through the inversion layer formed near back interface of sSi-channel. This vertical tunneling current shows high drain on current than lateral tunneling current because of high tunneling efficiency and these vertically tunneled electrons make an n-source at beneath the Ge-source and near back interface of sSi channel. However, the sSi channel is mainly controlled by VG because of much thinner EOT of front gate insulators than that of BOX. Consequently, this positive VB-induced vertical tunneling is greatly promising to improve the performance of Ge/sSi TFETs and it can be effectively utilized for improving the TFET performance by applying the synchronized VB with VG in multi-gate structure such as Fin FET, nanowire and so on.2. Drain engineeringIt is experimentally confirmed that the modified drain doping concentration of 1018 cm-3 is suitable for further performance improvement.3. EOT scalingIn this study the EOT was scaling from 2.5 nm to 1.5 nm by changing the gate dielectric material from Al2O3 to HfO2. It is found that higher on current is obtained in thinner EOT device. However, the leakage current increases in HfO2-device because of large Dit with Ge and Si.