GaSb nanowire transistors with process induced strain

Sammanfattning: With the constant downscaling of Si transistors reaching its limits, other alternatives have been actively researched the past decades. Group III-V semiconductors are excellent materials with generally high carrier mobilities that can replace Si in transistors. Strain has been used for some years to improve silicon technology, and it can also be applied to III-V materials to make them perform even better. In this work, GaSb nanowire transistors were strained using PECVD to deposit a stressing film of Si3N4 and the effects on the electrical characteristics investigated. The deposited films ranged between thicknesses of 40-104 nm, with stresses in the range 300-2000 MPa. Raman spectroscopy measurements showed a strain in the nanowires up to 0.5%. The effect on the threshold voltage from the Si3N4 films containing positive charges made it challenging to separate the effects from this and the effects from strain. All samples exhibited a reduction in current but a signicant increase in the on/off-ratio, making the strained devices turn off much better than untreated devices, with an on/off-ratio increase of up to 70 times observed. The results obtained here show that this method of process induced strain could see uses in order to reduce power consumption.