The characterization and passivation of fixed oxide charges and interface states in the Al2O3/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