Fast-Neutron Bombardment of GaSb

Abstract

Fast-neutron irradiation decreases the carrier concentration of polycrystalline samples of $n$- and $p$-type GaSb, indicating the production of low-lying traps. Vacuum heat treatment evidently removes such traps but also introduces additional acceptors, indicating a different rate of annealing for bombardment produced interstitial and vacancy atoms. Irradiation and heat treatment of $n$-type GaSb therefore results in the production of material of lower carrier concentration and reirradiation results in the conversion to $p$-type material. Repeated irradiations followed by heat treatments, however, do not reduce the net effective concentration of electrons in $n$-type material below ∼5×${10}^{17}$ ${\mathrm{cm}}^{-3\mathrm{}}$. The mobility of all samples is decreased by bombardment. Heat treatment subsequent to irradiation increases the mobility of $n$-type material but decreases the mobility of $p$-type samples still further below the decrease produced by bombardment. Low-temperature (-125°C) irradiation and subsequent warm-up and cool-down curves indicate the presence of defects of low thermal stability. No evidence was obtained for regions of low resistivity resulting from superlattice disordering as a result of quenching as might be expected from the thermal spike picture. The type and position of fast-neutron-introduced lattice defects is discussed with relation to previous models for Ge and InSb.