Monolithic transformer with underlying deep silicon-oxide block - Electronics Letters

Study of gate length dependent effective velocity manifests the velocity overshoot effects in MOSFETs. Effective velocity of holes in control Si, S i ~ . s G e ~ . ~ and Sio.793Geo,2Co.oo7 devices with different channel lengths are shown in Fig. 2. As channel length decreases, vef increases in every device. In the case of the 0.8 pm device, the effective hole velocity of Sio.793Ge0.2C0.007 is enhanced by 25.8% and 103% compared to Sio.sGeo,2 and control Si devices, respectively. The value veri of holes in the control Si device is in good agreement with the reported one [7, 81. The highest hole velocity in the Sio.$3eo.2 p-MOSFET of 8x lo6 cm/s as reported by Ansaripour et al. [8], is comparable with our binary device data. Note the substantial increase of the effective velocity as the devices are scaled down, which may be due to the onset of hole velocity overshoot. This has also been reported by Kaya et al. [9], even in 1.5 pm Sio.aGeo,z devices. As shown in Fig. 2, the effective hole velocity of the Si0.793Ge0.2Co.007 inversion layer exceeds IO’ cm/s in the shortest channel device (L = 0.8 pm). This is attributed to the hole velocity overshoot [7-91, which is considerably larger in the SiGeC device compared to the SiGe and control Si Conclusions: We have investigated the velocity-field characteristics of holes in partially strain compensated Sio,793Geo.2Co 007 p-MOSFET devices. The increase of high-field hole velocity in SiGeC shortchannel devices in the region of non-equilibrium transport is attributed to higher mobility owing to reduced process induced strain relaxation in C-containing alloy. Therefore, in addition to the improvement of hole mobility in low-field transport, our results indicate the benefit of an early onset of velocity overshoot in short channel SiGeC devices.