The effect of substrate temperature on the isolation of n-type GaAs layers using MeV boron implantation

The evolution of sheet resistivity (Rs) with annealing temperature in n-type GaAs layers irradiated with 11B+ at different target temperatures has been investigated. The n-type material was prepared using multi-energy implants of 29Si+ ions. An isolation region was formed using boron ions at single energy of 1.5 MeV with doses of 2×1014 cm-2 into samples held at RT, 100 and 200 °C. Sample resistivity was measured at room temperature both before and after annealing in the temperature range 350-800 °C. Maximum resistivity values were achieved after annealing at 500 °C for all three sets of samples. Annealing at higher temperatures returned the resistivity to a value close to that of the starting material and this recovery of conductivity was fastest in case of RT implants. Formation of thermally stable defects at high target temperatures was thought to be responsible for the different evolution trend of sheet resistivity with annealing temperature in samples irradiated at 100 and 200 °C compared to those irradiated at RT.