Implant isolation in GaAs device technology: Effect of substrate temperature

Abstract

Protons (H 2 +), boron (B +) and oxygen (O +) ions were used to isolate n-type GaAs layers at RT, 100 and 200 °C. Prior to the carrier removal implants, the n-type region was formed using keV multiple-energy implants of 29 Si + ions. 0.5–2 MeV isolation implants were performed at fluences around 1–3×10 14 cm −2 to create an almost uniform damage profile over ∼0.5 μm. This procedure placed the heavily damaged region associated with the end of the H 2 + , B + or O + ions range well into the semi-insulating GaAs substrate. The evolution of sheet resistivity ( R s) as a function of annealing temperature was studied in all cases. It is observed that the RT implants recover quicker to their pre-implanted sheet resistivity values for proton- and boron-isolated GaAs layers. In both cases, the thermal stability is improved as the implant temperature is increased which is due to the formation of thermally stable defects during implantation. The effect of enhanced dynamic annealing is also investigated which introduces higher as-implanted resistivity values for proton-implanted samples maintained at 100 or 200 °C during implantation. No such improvement in thermal stability due to hot implants, or any noticeable effect of dynamic annealing is found in oxygen-implants at either RT or elevated substrate temperatures. Compensation introduced in this case is a product of both damage related centres and oxygen itself.