The interplay between damage- and chemical-induced isolation mechanism in Fe+-implanted AlGaN/GaN HEMT structures

Authors:

• Karolina Pągowska,
• Maciej Kozubal,
• Andrzej Taube,
• Renata Kruszka,
• Maciej Kamiński,
• Norbert Kwietniewski,
• Marcin Juchniewicz,
• Anna Szerling

Abstract

This work presents the development of Fe ion implantation processes for the fabrication of thermally stable isolation of AlGaN/GaN high electron mobility transistors (HEMTs). Experiments, carried out by the triple Fe+ implantation into AlGaN/GaN HEMT epilayers on sapphire substrates, showed that it is possible to fabricate device isolation that is stable up to the temperatures typical for the formation of ohmic contacts to the AlGaN/GaN heterostructure. Thermal stability of the formed isolating regions was tested by electrical measurements on cTLM test structures, in a wide range of annealing temperatures (400–1100 °C) and concentration of Fe atoms of 1x10^18 cm−3 and 1x10^19 cm−3. Sheet resistance values over 1x10^15 have been achieved. The obtained highly resistive isolation was thermally stable up to the temperature of 1100 °C. Moreover, after annealing at the temperature of 1000 °C and 1100 °C the sheet resistance of implanted regions was almost an order of magnitude larger than previously presented in the literature. Due to the mastering of the technology of making thermally stable isolation through Fe ion implantation, it will be possible to raise the thermal budget and increase the flexibility in the design of individual steps in the fabrication process of AlGaN/GaN HEMTs.