Recent Progress in Implantation and Annealing of GaN and AlGaN

Abstract

Heterostructure modulation doped transistors (MODFETs) based on AlGaN/GaN structures have demonstrated impressive DC and microwave performance often despite high transistor access resistance. One approach to reducing the access resistance is to use selective area Si-implantation. While several reports exist on Si-implantation in GaN, little work has been done on implantation in AlGaN. In addition, more information on the annealing of implantation damage in GaN is needed to optimize its use in FETs and thyristors.

We report the electrical and structural properties of Si-implanted Al_0.15Ga_0.85N based on Hall measurements and Rutherford Backscattering (RBS) spectra, respectively. Al_0.15Ga_0.85N shows less damage accumulation than GaN for a room temperature Si-implant dose of 5×10¹⁵ cm⁻² based on the minimum channeling yield (26% for AlGaN as compared to 34% for GaN), however, as with GaN, this damage is difficult to remove by thermal annealing at °C.

We also report on high pressure (up to 15 kbar) and high temperature (up to 1500 °C) annealing for Si-implanted GaN. At 1250 °C ~50% electrical activation is achieved which increases to ~90% at 1500 °C. The photoluminescence of these samples is also restored, or even enhanced, by the high temperature treatments. Furthermore, RBS demonstrates that complete removal of the implantation induced damage is achieved for the 1500 °C anneal.