researchers based at purdue university have demonstrated the effectiveness of a gallium oxide on insulator field effect transistor (gooi) that could be used in ultra-efficient switches for power electronics and could potentially have significant environmental impacts through better control of electrical energy in circuits.

the schematic at left shows the design for an experimental transistor made of a semiconductor called beta gallium oxide,
which could bring new ultra-efficient switches for applications such as the power grid, military ships and aircraft.
at right is an atomic force microscope image of the semiconductor. (purdue university image/peide ye)

the gooi is especially impressive because of its ultra-wide bandgap, which is important in high-voltage applications, according to a report from the school. the gooi also has a higher breakdown voltage and researchers claimed to have “achieved electrical currents 10 to 100 times greater than other research groups working with the semiconductor.”

in addition to testing the new transistor, the researchers also developed a method for peeling layers of semiconductor from a single crystal using adhesive tape (similar to how graphene was discovered).

this method for creating beta gallium oxide is far cheaper than the standard method of epitaxy.  and can be used to cut it into belts or nanomembranes that can be placed on silicon disc for manufacturing into devices. it also created very smooth films with a surface roughness of only 0.3 nanometers.

the work will be published this month in ieee electron device letters. the research paper is currently available from the university and the abstract of the report read:

“in this letter, we report on high performance depletion/enhancement (d/e)-mode β-ga₂o₃ on insulator (gooi) field-effect transistors (fets) with record high drain currents (i_d) of 600/450 ma/mm, which are nearly one order of magnitude higher than any other reported i_d values.

“the threshold voltage (v_t) can be modulated by varying the thickness of the β-ga2o3 films and the e-mode gooi fet can be simply achieved by shrinking the β-ga₂o₃ film thickness. benefiting from the good interface between β-ga₂o₃ and sio2 and wide bandgap of β-ga₂o₃, a negligible transfer characteristic hysteresis, high i_don/off ratio of 10¹⁰, and low subthreshold swing of 140 mv/dec for a 300 nm thick sio₂ are observed.

“e-mode gooi fet with source to drain spacing of 0.9 μm demonstrates a breakdown voltage of 185 v and an average electric field (e) of 2 mv/cm, showing the great promise of gooi fet for future power devices.”