Oxygen thermal double donors

Shallow donors (or acceptors) add new electrons to the CB (or new holes to the VB), resulting in a net increase in the number of a particular type of charge carrier. The implantation of shallow donors or acceptors is performed for this purpose. But this process can also occur unintentionally. For example, the precipitation aroimd 450°C of interstitial oxygen in Si generates a series of shallow double donors called thermal donors. As-grown GaN crystal are always heavily n type, because of some intrinsic shallow-level defect. The presence and type of new charge carriers can be detected by Hall effect measm ements. 

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