The Characterization and Passivation of Fixed Oxide Charges and Interface States in the $\hbox{Al}_{2}\hbox{O}_{3}/ \hbox{InGaAs}$ MOS System

In this paper, we present a review of experimental results examining charged defect components in the Al
₂
O
₃
/In
_0.53
Ga
_0.47
As metal-oxide-semiconductor (MOS) system. For the analysis of fixed oxide charge and interface state density, an approach is described where the flatband voltage for n- and p-type Al
₂
O
₃
/In
_0.53
Ga
_0.47
As MOS structures is used to separate and quantify the contributions of fixed oxide charge and interface state density. Based on an Al
₂
O
₃
thickness series (10-20 nm) for the n- and p-type In
_0.53
Ga
_0.47
As layers, the analysis reveals a positive fixed charge density ( ~ 9 ×10
¹⁸
cm
^-3
) distributed throughout the Al
₂
O
₃
and a negative sheet charge density (- 8 × 10
¹²
cm
^-2
) located near the Al
₂
O
₃
/In
_0.53
Ga
_0.47
As interface. The interface state density integrated across the energy gap is ~1 ×10
¹³
cm
^-2
and is a donor-type (+/0) defect. The density of the fixed oxide charge components is significantly reduced by forming gas (5 % H
₂
/ 95% N
₂
ambient at 350 °C for 30 minutes) annealing. The interface state distribution obtained from multi-frequency capacitance-voltage and conductance-voltage measurements on either MOS structures or MOSFETs indicates a peak density located around the In
_0.53
Ga
_0.47
As midgap energy, with a sharp increase in the interface state density toward the valance band and evidence of interface states aligned with the In
_0.53
Ga
_0.47
As conduction band. The integrated interface state density obtained from multi-frequency capacitance-voltage and conductance-voltage analysis is in good agreement with the approach of comparing the flatband voltages in n- and p -type Al
₂
O
₃
/In
_0.53
Ga
_0.47
As MOS structures. Finally, this paper reviews recent work based on an optimization of the In
_0.53
Ga
_0.47
As surface preparation using (NH
₄
)
₂
S, combined with minimizing the transfer time to the atomic layer deposition reactor for Al
₂
O
₃
, which indicates interface state reduction and genuine surface inversion for both n- and p -type Al
₂
O
₃
/In
_0.53
Ga
_0.47
As MOS structures.