Fabrication of diamond modulation-doped FETs by NO₂ delta doping in an Al₂O₃ gate layer

We demonstrated modulation doping in diamond and fabricated diamond field-effect transistors (FETs) by NO 2 p-type delta doping in an Al 2 O 3 gate layer. We confirmed modulation doping effects: a spatial separation between the NO 2 acceptors in the Al 2 O 3 gate insulator and the hole channel on the diamond surface increased the hole mobility, and the high hole sheet concentration was maintained till high temperatures. The diamond FETs showed maximum drain current density of −627 mA mm −1 , and transconductance of 131 mS mm −1 . The mobility increased to 2465 cm 2 V −1 · s −1 near the threshold voltage, and the Baliga’s figure-of-merit was 179 MW cm −2 .