Properties of Surface Imperfections Produced on Germanium by Cleaning Treatments

Abstract

Surface conductivity and Hall coefficient of germanium cleaned by ion-bombardment and subsequent annealing have been measured over the temperature range 1.5–300°K. The results indicate that donor levels are produced near the surface by ion-bombardment and are eliminated with subsequent annealing at 500°C in high vacuum making the surface space charge layer p-type. The density of the excess holes near the surface has a magnitude of 8×10¹¹ cm⁻² for an n-type of 8Ω cm and 8.5×10¹⁰ cm⁻² for a p-type of 20Ω cm. Ion-bombardment gives rise to a small Hall maximum at low temperatures around 5°K. This maximum shifts to higher temperatures as annealing treatments are repeated and disappears if air is introduced. This maximum is attributed to holes of the order of 10⁷ cm⁻² in the space charge layer.