The Comparison of Current Ratio $I_{\mathrm{\scriptscriptstyle ON}}/I_{\mathrm{\scriptscriptstyle OFF}}$ and Mobility Between SiGe Substrate and GaAs Substrate In0.23Ga0.77As Channel MOSFETs

This paper mainly describes the comparison of I
_ON
/I
_OFF
ratio and mobility between SiGe substrate and GaAs substrate In
_0.23
Ga
_0.77
As channel MOSFETs grown by metalorganic chemical vapor deposition. In order to make the comparison more reasonable, we choose the same size (Lg = 10 μm) for both the SiGe substrate and GaAs substrate MOSFETs. As for the SiGe substrate MOSFETs, its highest ON-current to the lowest OFF-current (I
_ON
/I
_OFF
) ratio is less than 1×103, while that of GaAs substrate MOSFETs are up to 4×10
⁴
(both at a gate bias of 3 V). Due to the Ge diffusion into the InGaAs channel, it will make the intrinsic channel become an n-type doped semiconductor and then influence the pinchoff characteristics. The maximum effective mobility of SiGe substrate MOSFETs is 1800 cm
²
/V · s and that of GaAs substrate MOSFETs is up to 2090 cm2/V · s. The main reason for the higher mobility of GaAs substrate MOSFETs is maybe due to its smaller density interface trap density Dit and undoped InGaAs channel. Through comparing the performance, particularly the I
_ON
/I
_OFF
ratio and mobility between SiGe substrate and GaAs substrate MOSFETs, we aim to find out some feasible methods to improve the performance of InGaAs channel MOSFETs on SiGe substrate.