1. A method comprising: obtaining a substrate including a first semiconductor layer and first and second electrically insulating layers, the semiconductor layer being between the first and second electrically insulating layers; removing a portion of the first semiconductor layer, thereby forming a space between the first and second electrically insulating layers; growing a channel layer containing quantum structures in the space such that the quantum structures are functional as ambipolar traps; patterning one of the first and second electrically insulating layers, thereby exposing a surface of the channel layer, and epitaxially forming a source/drain structure including p+ and n+ regions on the exposed surface of the channel layer and configured to inject both electrons and holes into the channel layer.