Reduction in interface state density of Al2O3/InGaAs metal-oxide-semiconductor interfaces by InGaAs surface nitridation

We report the decrease in interface trap density (D-h) in Al2O3/InGaAs metal-oxide-semiconductor (MOS) capacitors by using electron cyclotron resonance plasma nitridation of the InGaAs surfaces. The impact of the nitridation process on the MOS interface properties is quantitatively examined. The plasma nitridation process is observed to form a nitrided layer at the InGaAs surface. The nitridation using microwave power (P-microwave) Of 250 W and nitridation time (t(nitridation)) of 420s can form Al2O3/InGaAs MOS interfaces with a minimum D-it value of 2.0 x 10(11) cm(-2) eV(-1). On the other hand, the nitridation process parameters such as P-microwave and t(nitridation) are found to strongly alter D-it (both decrease and increase are observed) and capacitance equivalent thickness (CET). It is found that the nitridation with higher P-microwave and shorter t(nitridation) can reduce D-it with less CET increase. Also, it is observed that as t(nitridation) increases, D-it decreases first and increases later. It is revealed from XPS analyses that minimum D-it can be determined by the balance between the saturation of nitridation and the progress of oxidation. As a result, it is found that the superior MOS interface formed by the nitridation is attributable to the existence of oxide-less InGaN/InGaAs interfaces. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4755804]