Space-Charge Currents in Gallium Arsenide

Abstract

Mott and Gurney¹ pointed out that an insulator should be able to carry an electronic current if electrons were injected into it by a suitable contact. Such currents were observed experimentally by Smith and Rose² in cadmium sulphide crystals. They showed that an essential condition was that the ‘deep trap’ density should be low, deep traps being centres with energy-levels well below the conduction band which can accept electrons. In a recent communication³ a model was proposed to account for the properties of semi-insulating gallium arsenide. The model suggested that in this material the above condition should be satisfied, and as a result it was predicted that space-charge currents should be observable. Here we present experimental results confirming the correctness of the prediction.