Near‐band‐edge absorption and positron trapping under illumination in semi‐insulating GaAs: Role of As vacancies

We show that positron trapping at negative As vacancies revealed under illumination in bulk semi‐insulating GaAs correlates with a form of near‐band‐edge absorption known as reverse contrast (RC). We conclude that it is the ionization of As vacancies to their negative charge state that gives rise to RC absorption.