Capítulo 2: El diseño de accesorios y sus componentes
2.1 Materiales, estilos y colores en el diseño de accesorios sustentables
In this subsection, the data obtained using the tting of the Cg-Vg characteristic and Maserjian
Y -function (Figure 4.6) is compared to the results obtained with conventional methods such as the Berglund integral [28], the Terman method [29], the high-low method [30] and the full conductance method [8]. It is important to note here that these methods were only applied after the data extraction based on the tting the Cg-Vg and Maserjian Y -function was performed,
indicating that the extraction process was not biased by any preliminary analysis.
Figure 4.7(a) compares the band bending vs Vg obtained using the tting of the Cg-Vg and
Maserjian Y-function, the Terman method [29] and the Berglund integral [28]. While the data used with the Terman method is the same as that used for the tting (i.e.: Cg-Vg measured
at f = 1 MHz and T = -50◦C), the data used in the calculation of the Berglund integral is a
Cg-Vg characteristic measured at f = 200 Hz and T = 25◦C (not shown)5. Excellent agreement is
obtained between the tting method and the Terman method. However, a signi cant discrepancy between the Berglund integral and the other methods is observed. For Vg going from 0.4 V to
-0.4 V, the Berglund integral indicates a less e cient band bending than the other methods. This could be attributed to the fact that the Dtrap response near the band edges could not be
frozen out at f = 1 MHz and T = -50◦C, leading to an overestimation of the band bending
e ciency near the band edges with the methods relying on an estimate of the H-F Cg-Vg response
(i.e.: tting method and Terman method), consistent with [31]. For Vg > -0.4 V, the Berglund
integral severely overestimates the band bending e ciency, suggesting that the f of 200 Hz is not su ciently low to obtain a full response of the interface traps located near the middle of the In0.53Ga0.47As bandgap. This is in agreement with [7], where the use of a f as low as 40 Hz is
recommended to maximize the Dtrap response.
Figure 4.7(b) compares the Dtrap(E) pro le obtained with the tting method to the pro les
extracted with the Terman, high-low and full conductance methods. The excellent agreement
5The Cg-Vgcharacteristic is corrected for parasitic capacitance using the method reported in [17]. This method requires the measurement of a device with a long gate length and a device with a short gate length. The small gate area of the short gate-length device, the lowest f giving acceptable noise level was 200 Hz.
Figure 4.7: (a) Comparison of the band bending E-EV vs Vg pro le obtained with the tting
of the Cg-Vg characteristic and Maserjian Y -function to the pro le obtained with the Terman
method [29] and Berglund integral [28]. (b) Comparison of the trap density vs energy pro le obtained with the tting method to the pro les extracted from the Terman (the short dash curve shows the intrapolation of the Terman data), high-low [30] and full conductance [8] methods. Cox/q is indicated to highlight the limitation of the full conductance method. The grey shaded
4.5. Conclusion between the tting method and the Terman method is consistent with the analysis of the band bending shown in Figure 4.7(a). For E-EV going from 0.5 eV to 0.73 eV, it is clear that the
tting method and the Terman method underestimate Dtrap. The high-low and the conductance
methods, however, show reasonable agreement in this energy range, where Dtrap decreases from
5.8 × 1012 /cm2.eV to 4.2 × 1012 /cm2.eV. For E-E
V < 0.5 eV, the high-low method under-
estimates Dtrap as it suers from the same limitation as that observed in the analysis of the
Berglund integral [Figure 4.7(a)]. The conductance method also underestimates Dtrap in this
energy range. This underestimation is consistent with recent works [8, 31] reporting Dit un-
derestimation with the conductance method in the case of Dit values exceeding Cox/q. This is
the case in our devices since Cox/q = 4.75 × 1012 /cm2.eV and the tting method indicates a
mid-gap Dit feature peaking at 1.5 × 1013 /cm2.eV.
4.5 Conclusion
The xed oxide charges and interface/border traps present in the Al2O3/In0.53Ga0.47As MOS-
FETs presented in Chapter 3 were examined through the study of the full gate capacitance Cg-Vg
characteristic. The Cg-Vg characteristic was measured at a f of 1 MHz and a T of -50◦C in order
to approximate a true H-F response. The comparison of the measured Cg-Vg characteristic with
a theoretical (ideal) H-F characteristic yielded a N+of 1.2 × 1012/cm2along with an integrated
Dtrap across the In0.53Ga0.47As bandgap of 1.2 × 1013 /cm2.
The tting of the Cg-Vg characteristic and corresponding Maserjian Y -function yielded a
Dtrap(E) across the In0.53Ga0.47As energy gap and extending into the In0.53Ga0.47As conduction
band. This analysis revealed donor-like (+/0) traps within the In0.53Ga0.47As bandgap, with a
peak density of ∼ 1.5 × 1013 /cm2.eV and centered at 0.36 eV above the In0.53Ga0.47As E V. A
sharp increase in donor-like (+/0) trap density in the energy range of 0.1 eV to 0.2 eV above the In0.53Ga0.47As EV was also observed. The analysis also indicated acceptor-like (0/-) traps
located at energy levels aligned with the In0.53Ga0.47As conduction band, with a density of ∼
2.5 × 1013 /cm2.eV at 0.3 eV above the In0.53Ga0.47As EC. Although the tting could reveal
whether the observed traps were donors or acceptors, this method could not to discern whether these traps were interface traps, border traps, or a combination of both.
Finally, excellent agreement with the conventional Terman method was obtained. However, the comparison with the high-low and conductance methods highlighted a Dtrapunderestimation
near the In0.53Ga0.47As band edges. This issue may be addressed through the measurement and
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Investigation of Border Traps and
Mobility
5.1 Introduction
InGaAs and related compound semiconductors have become serious candidates for replacing strained Si in future complementary metal-oxide-semiconductor (CMOS) device applications due to their remarkable electron mobility [1]. The standard method for extracting the eective mobility (µef f) in a metal-oxide-semiconductor eld-eect transistor (MOSFET) relies on a
gate-to-channel split capacitance-voltage (C-V) measurement combined with a measurement of the drain current (Id) vs gate voltage (Vg) characteristic in direct current (DC) [2]. While
this method enables highly accurate µef f extraction on SiO2/Si MOSFETs, its accuracy when
applied to emerging high-k/InGaAs devices, with relatively high density of interface traps (Dit)
and density of border traps (Dbt), becomes questionable. In an attempt to address this issue,
we investigated the use of an alternative method based on the inversion-charge pumping (ICP) and pulsed Id-Vg measurements, rst proposed by Kerber et al. for Si based MOSFETs in [3],
for the µef f extraction of surface-channel Al2O3/In0.53Ga0.47As MOSFETs.