Abstract
A study of ion implanted zinc in GaAs has been made using four annealing techniques: e-beam, graphite strip heating, furnace annealing in an arsine ambient and laser annealing. The highest hole concentrations, 7-8 x 10[19]cm[-3] were obtained using electron beam annealing. Graphite strip heating and electron beam annealing were able to electrically activate 100% of the implanted dose. Laser annealing produced surface decomposition during irradiation which was reduced by using a diffuser. The effect of strain on the activation of the zinc has been demonstrated by comparing chemical vapour deposited Si[3]N[4] with reactively evaporated AIN encapsulants. A model for the activation of zinc in GaAs has been formulated to take into account the different annealing techniques used for solid phase recrystallisation. The electrical and structural properties of 1 x 10[14] Se[+]cm[-2], 100-400 kV and 5 x 10[12] Se[++]cm[-2], 350 kV implants into (100) semi-insulating GaAs have been studied. Peak carrier concentrations of 5 x 10[18] cm[-3] have been measured and mobilities of 4000 cm[2]V[-1]s[-1] obtained for low dose implants (n = 1-2 x 10[17]cm[-3]) by annealing samples on a graphite strip heater. Si[3]N[4] and AIN have been used as encapsulants. Comparisons are made with capless annealing in an arsine ambient. A model for the activation of selenium in GaAs relates the activation energy of diffusion with the rate of electrical activation of selenium.