Thermally stable device isolation by inert gas heavy ion implantation in AlGaN/GaN HEMTs on Si

Abstract

Multiple energies of heavy ion implantation with inert-gas ion (84Kr+) were carried out on AlGaN/GaN high-electron-mobility transistors (HEMTs) for planar device isolation. Thermal stability of the implantated samples were also investigated by isochronal annealing at 500, 600, 700, and 800 °C (each temperature for 1 h.). Due to the damages created by heavy ions (84Kr+) in the GaN lattice, the implant-isolated Al0.27Ga0.73N/GaN HEMT samples exhibited better thermal stability than 40Ar+-implant-isolation. This was also confirmed by Rutherford backscattering spectrometry in channeling condition and ultraviolet micro-Raman spectroscopy measurements. With reference to mesa-isolated AlGaN/GaN HEMTs, the buffer breakdown voltage is also stable in the implant-isolated AlGaN/GaN HEMTs. An enhanced OFF-state breakdown voltage was also realized in the implant-isolated AlGaN/GaN HEMTs. The inert gas heavy ion implantation (84Kr+) is a viable solution for the fabrication of thermally stable planar AlGaN/GaN HEMTs even up to 800 °C under long-term isochronal annealing.

Improved planar device isolation in AlGaN/GaN HEMTs on Si by ultra-heavy 131 Xe+ implantation

“…The observation of enhanced BV gd from implant-isolated HEMT is due to the low gate leakage current. Similar observation has also been realized in AlGaN/GaN HEMTs by Ar þ and Kr þ implantation [5]. P. Liu et al, observed an elimination of gate leakage by placing plasma enhanced tetraethylorthosilicate (PE-TEOS) oxide spacers in between gate and mesa sidewalls [25].…”

“…Inter‐device isolation of AlGaN/GaN HEMTs is typically achieved by mesa etching techniques using inductively coupled plasma (ICP) or reactive ion etching (RIE) and BCl 3 /Cl 2 as plasma source. Due to the presence of mesa sidewall in the conventional mesa‐isolation process, the metal gate as well as the passivation layer are in contact with 2‐dimensional electron gas (2DEG) of AlGaN/GaN HEMT structure, which leads to higher gate leakage current and non‐uniformity in buffer breakdown voltage with passivation layer . Moreover, the AlGaN/GaN wafer after mesa‐isolation exhibits a non‐planar surface, which in return affects the process yield of device.…”

“…In order to avoid the problems introduced by plasma etching, implantation isolation by various ion species, such as N + , P + /He + , O + , Fe + , Ar + , Kr + , etc., has been studied to realize planar AlGaN/GaN HEMTs. However, it was observed that most of the ion species are not able to maintain the high resistivity of implanted region after high temperature annealing except for Fe + and Kr + . The sheet resistance ( R sh ) of P + /He + implanted region was even reported to decrease by ∼6 orders of magnitude after 900 °C annealing .…”

The effect of ion implantation on structural damage of сompositionally graded AlGaN layers

“…3 After the implantation, an almost uniform depth distribution of hydrostatic strain in the Al x Ga 1-x N layers the most correctly describes the Al x Ga 1-x N peaks on the (0002) 2θ/ω scan. This is despite the high implantation energy (100 keV) that should have resulted in the maximum concentration of Ar + at the depth of about 90 nm from the surface [19], which is often reported for ion implantation into single crystals [26]. The strain in the GaN buffer increases only after the implantation with the first dose of Ar + ions and is not affected by the second dose.…”

Impact of rapid thermal annealing on Mg-implanted GaN with a SiO x /AlN cap-layer

“…However, these diodes require the processing of guard rings to avoid the presence of the high electric field under the Schottky contact causing the early breakdown of the diodes. Implantation of many species such as B , Mg , Mg/P , Kr, and Ar have been studied to achieve those guard rings. Good results were achieved with an Mg implantation step and a high temperature annealing, above 1100 °C, to create and activate p‐type doped guard rings .…”