Impact of doping profile on electrical performance of boron-doped diamond metal–oxide–semiconductor field-effect transistors

Electrical characteristics of boron-doped diamond (B-diamond) metal–oxide–semiconductor field-effect transistors (MOSFETs) fabricated on an epitaxial layer with a thickness (tboron) of 1514 nm and a boron doping concentration (Nboron) level of 1017 cm−3 are investigated. For the as-fabricated B-diamond MOSFET operating at room temperature (298 K), the maximum absolute drain current (|ID,max|) is 4.7 mA/mm. At elevated temperatures of 573 and 673 K, the |ID,max| values increase to 76.9 and 109.2 mA/mm, respectively. The threshold voltage (VTH) values for B-diamond MOSFETs operating at 298, 573, and 673 K are 320.2 ± 5.0, 1143.2 ± 20.0, and 895.1 ± 20.0 V, respectively. Post-annealing at 773 K for 30 min, |ID,max| and VTH measured at 298 K improve to 6.0 mA/mm and 258.7 ± 5.0 V, respectively. Capacitance–voltage measurements indicate that the annealing process improves the dielectric property of the Al2O3 insulator and reduces the interfacial border traps, fixed charge density, and trapped charge density in the Al2O3/B-diamond MOS capacitor. The impact of the doping profile on the electrical performance of B-diamond FETs is summarized. At a constant Nboron level, both |ID,max| and VTH increase with increasing tboron. On the other hand, at a similar tboron, these parameters increase with higher Nboron.