Search

Electrical activation studies of Si-implanted GaN layers on sapphire were made as a function of annealing temperature (1100–1400 °C). For an ion dose of 1.0×1014 cm-2, the optimum annealing temperature was 1400 °C, exhibiting a nearly 100% electrical activation efficiency and a low sheet resistance of ∼450 Ω/square at room temperature. From variable temperature Hall-effect measurements, Si-implanted GaN films annealed below 1200 °C displayed deep ionization levels of ∼280 meV, whereas samples annealed above 1300 °C had shallow ones of ∼11 meV. For lateral Schottky diodes fabricated on Si-implanted GaN layers annealed below 1200 °C, capacitance frequency and thermal admittance measurements showed a typical dispersion effect characteristic of a single deep donor with an activation energy of ∼133 meV. These results illustrate that deep donor levels created by the Si implantation in GaN layers apparently annihilate and transit to shallow levels produced by the Si ion substitution for Ga in the GaN lattice (SiGa) by annealing at temperature greater than ∼1300 °C at these doses. [ABSTRACT FROM AUTHOR]

The fabrication of GaN merged p–i–n/Schottky (MPS) diodes using Si+ ion implantation into p-epi layers on bulk, free-standing GaN substrates is reported. Diode diameters from 50 to 500 μm were investigated. These initial MPS diodes show larger turn-on voltage (∼30 V) than the unimplanted p–i–n diodes (∼10 V) fabricated on the same wafer but lower reverse leakage current density. The Si+ implant activation efficiency is ∼25% for 1150 °C anneals, reaching ∼30% for 1200 °C anneals. [Copyright &y& Elsevier]

Type conversion of p-GaN by direct Si+ ion implantation and subsequent annealing was demonstrated by the fabrication of lateral Schottky diodes. The Si+ activation percentage was measured as a function of annealing time (30--300 sec) and temperature (1,000--1,200°C), reaching a maximum of ∼30% for 1,200°C, 2-min anneals. The resulting n-type carrier concentration was 1.1 x 1018 cm-3 for a moderate Si+ ion dose of ∼2 x 1014 cm-2. The lateral Schottky diodes displayed a negative temperature coefficient of -0.15 V.K for reverse breakdown voltage. [ABSTRACT FROM AUTHOR]

Si+ ion implantation at a total dose of 1.0×1015 cm-2 and multiple ion energies in the range of 30–190 keV into Al0.13Ga0.87N layers on sapphire substrates for n-type doping was carried out at substrate temperatures ranging from -196 to 700 °C, followed by annealing at 1150–1400 °C for 5 min. The activation efficiency at fixed annealing temperature (1250 °C) was highest (∼50%) for room temperature implantation and degraded significantly for elevated temperature implantation. The effective Si donor ionization energy decreased with increasing annealing temperature, which may be related to the Mott transition that creates degenerate layers as the activation percentage increased. The minimum sheet resistance obtained was ∼100 Ω/sq after annealing room temperature implants at 1350–1400 °C. [ABSTRACT FROM AUTHOR]

The electrical activation characteristics of implanted Si[sup +] in GaN were investigated as a function of annealing temperature (1000 °C–1200 °C). The maximum activation percentage for an ion dose of 2.5×10[sup 14] cm[sup -2] was ∼30% with an apparent activation energy for electrical activation of 1.65±0.15 eV obtained from the temperature dependence of the saturated carrier density. Lateral Schottky diodes fabricated on this material showed forward ideality factors of ∼2 and a temperature coefficient of -0.15 V K-1 for their reverse breakdown voltage. These results show the feasibility of creating n[sup +] tubs in p-GaN such as are needed as sources of minority carriers to achieve inversion in GaN metal-oxide-semiconductor field-effect transistors. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]