Body doping dependence of field-effect mobility in both n- and p-channel 4H-SiC metal-oxide-semiconductor field-effect transistors with nitrided gate oxides

Abstract

Both n- and p-channel SiC MOSFETs, the gate oxides of which were annealed in NO, with various body doping concentrations were fabricated. Despite the large difference in bulk mobility between electrons (1020 cm2/Vs) and holes (95 cm2/Vs), the maximum field-effect mobility in heavily-doped (~5×1017 cm−3) MOSFETs was 10.3 cm2/Vs for the n-channel and 7.5 cm2/Vs for the p-channel devices. The measurements using body bias revealed that the field-effect mobility in both n- and p-channel SiC MOSFETs is dominated by the effective normal field rather than the body doping.

Study of Carrier Mobilities in 4H-SiC MOSFETS Using Hall Analysis

“…After distinguishing the dominant scattering mechanisms in these devices, Hall measurements were carried out under the effect of body bias ( V BS ) so that the Hall mobility ( ) can be studied as a function of transverse electric field in the strong inversion regime. Recent studies [ 13 , 14 ] observed the effect of transverse electric field on mobility in the strong inversion regime maintaining a fixed carrier concentration. A constant carrier concentration realizes fixed screening from scattering centers and enables the assessment of the sole effect of surface roughness scattering on mobility.…”

“…A schematic diagram of these two charge distributions is shown in the left panel of Figure 1 . In Equation (2), is a constant with a value of 0.5 for n-channel and for p-channel Si MOSFETs at [ 19 , 20 , 21 , 22 ], which are considered the same for 4H-SiC [ 13 , 14 , 23 , 24 ], but this choice does not affect the results and may need further studies in a wider effective field range. is the dielectric constant, q is the electron charge, is the free carrier concentration, and N A is the p-well substrate doping concentration for n-channel MOSFETs.…”

“…Recent studies [ 10 , 13 ] on 4H-SiC MOSFETs use field-effect mobility models to analyze channel transport. Additionally, research by Mikami et al [ 13 ] explored the importance of body bias and explained how a body bias experiment can provide predictions of transistor characteristics for MOSFETs made with higher or lower substrate doping using field effect mobility on the weak inversion region. However, the channel scattering mechanisms for p-channel 4H-SiC MOSFET remain unexplored using Hall analysis.…”

“…To this end, the channel mobility of nitric oxide (NO)-annealed n- and p-channel 4H-SiC MOSFETs in the strong inversion regime was characterized using Hall measurements. Measurements were performed using the body-bias technique, which allows variation of the effective electric field ( ) in the channel [ 13 , 14 ]. This approach allows one to differentiate and establish the dominant scattering mechanisms limiting carrier transport, in different carrier density and substrate doping regimes.…”

Mobility degradation under a high effective normal field in an inversion layer of 4H-SiC (0001) metal–oxide–semiconductor structures annealed in POCl3

“…This phenomenon cannot be interpreted simply on the basis of Coulomb scattering from acceptors in a p-type body. 23,24) Furthermore, the influence of scattering by trapped electrons is inevitable, 25) since numerous trapped electrons remain even after nitridation. Therefore, Coulomb scattering due to the trapped electrons and surface roughness scattering, which is dominant in the high-E eff region, are indistinguishable.…”